BY her own admission, Nina Nesbitt isn't much of a golfer.

So it's safe to say that her 20 years on this earth had also passed in blissful ignorance of the Ryder Cup until she received an invitation to perform at the concert marking the start of the biennial tournament.

"I'm not going to lie," she says, sitting cross-legged on a sofa in an Edinburgh hotel room. "I didn't really know much about it until I was booked for the concert. Then I was telling people I was doing it and everybody was going, 'Oh my God! The Ryder Cup!' So now I'm like: 'OK, so it's quite a big deal ...'"

Hostilities re-commence on fairway and green next Friday at Gleneagles as Europe's best golfers face off against their American counterparts. Two days earlier, however, Nesbitt will join Nile Rodgers, Texas, Amy Macdonald, Jake Bugg, Midge Ure, the Royal Scottish National Orchestra, Scottish Ballet and others on stage at Glasgow's SSE Hydro for the Ryder Cup 2014 Gala Concert, part of the ongoing Homecoming Scotland 2014 programme.

Young she may be, but the Edinburgh-born singer is no stranger to the big stage. She's already performed at the Usher Hall, undertaken an arena tour with mega-selling DJ/producer Example and - resplendent in a plaid jacket and black miniskirt - led the Tartan Army in a rousing rendition of Flower Of Scotland at Hampden Park ahead of a World Cup qualifier against Belgium last September.

"Hampden wasn't that scary for some reason," she laughs. "I expected to be really nervous but I wasn't. I think it was because it was so big it didn't feel real. I think the Example tour was the scariest thing I've done because I was really new to it all. It was just me and my guitar, I'd just turned 17, it was a rave crowd in an arena and nobody knew who I was. I was just trying to make an impression. But it went really well. The crowd was really receptive. They were up for it and it was so different from Example that it made them listen and pay attention."

Different it certainly was, but people have been listening and paying attention to the young Scot ever since. In 2012, for instance, when she digitally self-released The Apple Tree EP, which gave her a top 10 hit in the download charts after finding favour with Radio One. Or, after signing to music giant Universal, when she released Stay Out, a wry look at teenage nightlife which came accompanied by a video showing Nesbitt and a group of gal pals barrelling around Glasgow after dark. "She thinks she's in Barbados, but outside it's minus three," goes a typically barbed line.

Stay Out just missed the Top 20 but again it found its way onto Radio 1's all-important A-playlist, marking Nesbitt out as one to watch. It certainly caught the attention of retailer John Lewis, who asked her to record a cover of Fleetwood Mac's Don't Stop for a TV campaign.

Into 2014, and still only 19, Nesbitt released her debut album, Peroxide. It topped the album charts in Scotland and in its lead single she latched onto another zeitgeisty teen preoccupation: selfies.

In the song of the same name, she takes some of the ideas behind Smokey Robinson's The Tears Of A Clown and re-fashions them for the smartphone-toting social media generation. So in her version there's no attempt to put on a brave face in order to fool the public. Instead: "I strike a pose and tilt my chin and hold the light to suit my skin/Your favourite T-shirt on again … I'll post it up in black and white/With a depressing quote on my life." It's a neat conceit.

"I feel like between the ages of 17 and 20 you do a lot of growing up," she tells me. "Selfies is something I wouldn't relate to so much now, being a bit older. But at the time I felt it was something I could relate to and a lot of the fans could relate to as well."

Someone else who took early notice of Nesbitt is Ed Sheeran and the story of her first meeting with the platinum-selling singer-songwriter has now achieved a sort of folkloric status.

It's a story she's obviously told a lot so I sense I'm getting the abridged version. But essentially it runs like this: a friend of hers at radio station Forth One was organising a live studio session in Edinburgh with Sheeran and invited Nesbitt along. At the time, she was an aspiring singer-songwriter with only about a dozen pub gigs to her name and her friend thought she might get some pointers. She did, and a lot more besides.

"I went along and we just started chatting to each other," says Nesbitt. "I asked if he had any advice for singer-songwriters and he was like, 'Oh do you play guitar? Play me something.' So I did and the next day he invited me on tour, just like that."

And it was, literally, just like that. Before she could say, 'Let me think about it for a day or so', she found herself opening for Sheeran at the ABC in Glasgow. Big stage, big crowd, big nerves. Nesbitt and Sheeran later dated and it's not hard to guess the subject of the song Nina, from his 2014 album X. Nesbitt returned the favour in several songs on Peroxide, though she won't say which ones.

"The Example tour came straight after that, which was even scarier," she says, continuing the story. "So it was a very frantic time. And because I was so unaware of the music industry and how it worked I didn't really know what was going on. Looking back, it would have been good if it had happened when I was a little bit older and had more understanding of how things worked. I just thought you got up on stage and you needed a manager. But then I started discovering you had to have a lawyer and a publisher and an agent, and I had to get all those things within about a month."

Two years on and now relocated to London, Nesbitt is clearly a lot wiser about the music industry, the sudden celebrity it can confer and the challenges that come with it. She may still be only on the periphery of fame but she is certainly on the radar and you don't have to do too much digging before you find paparazzi shots of her.

Here she is out on the town with chart-topping singer Ellie Goulding, for instance, photographed for a tabloid which notes her "leggy look", "tailored black shorts" and "glittery knit". Here she is again at the Scottish Fashion Awards, looking "gorge" in a "gothic glam lace dress", according to website Sugarscape, which regularly pits her against the likes of Taylor Swift, Rita Ora and Pixie Lott in its best-dressed "fash-offs". "Gorge-manorge" is another Sugarscape-ism that gets applied to Nesbitt, whose Scandinavian good looks - inherited, presumably, from her Swedish mother - are an important part of her coming fashion icon status.

But is she wary of straying too far into that world, handing over too much of herself to the public gaze? She looks slightly taken aback by the question.

"I don't have a famous friend circle at all," she says, "but Ellie I've found is really nice and we get on really well. We both do a similar thing so it's been good to get to know her. But I'm not one of those people who hangs about with loads of famous people on nights out … It would bother me if someone followed every bit of my private life because I'm a pretty private person."

Of course privacy to a 20-year-old doesn't preclude Tweeting, FaceBooking, status updating and Instagramming on a regular basis. Nesbitt is one of generation of musicians whose early steps have been taken not on the stage of sweaty backstreet rock venues but on YouTube. It was there that she began posting cover versions and self-penned songs. Only later did she progress to playing them live.

"I was far too shy to perform them, so I thought if I put them on YouTube and don't tell anyone then if people like them maybe I can get up and perform them," she explains. "I started posting them and getting a few people saying they liked them, just randoms. So I started posting more and more, sharing them with friends."

Not everyone liked them, though. "When I got to school I got a lot of abuse for it. People just thought it was really bad and would write horrible stuff online."

She carried on regardless and set about trying to differentiate her videos from those of all the other bedroom guitarists emoting into camera lenses while strumming their way through songs by Mumford And Sons. Her solution? To take to the countryside around her home in Balerno, on the outskirts of Edinburgh, and perform unusual cover versions to be filmed by a friend. One of the songs she chose was by Example, which is how she came to the attention of the rapper and producer. But before you go looking, those videos are no longer up.

"I took them down," she says. "I didn't want to be seen as that girl that sang on YouTube, that girl that did covers. I wanted to be known for my own stuff and start being more of a proper musician and be taken more seriously. I wanted the first thing people saw to be my own music."

Now the only Nina Nesbitt you find on YouTube is the one in the glossy videos, the "proper musician" of Stay Out and Selfies, the one you can see rocking out in black leather at T in the Park backed by a three-piece band. She still tweets, though, and with 157,000 Twitter follows and counting it's clear she has a large and growing constituency. But has she had any Lily Allen-style Twitter spats yet?

"I'm quite an opinionated person and that can be a bad thing on social media," she admits.

Don't drink and Tweet is the best advice I can offer on that score I tell her. She laughs.

"I'm actually such a nice person when I'm drunk but, yeah, I purposefully make myself very bland on the internet because I can't be bothered with it. I'm not there to start arguments. If I have a strong opinion about something I'll keep it to myself or talk to my friends about it. I use Twitter as a way of getting my music out to my fans fast. It's not like I think my opinion is so important I have to get it out there and share it with everyone."

What she will share is a little information about her new album. Her debut came out in February but because many of the songs on it were old (a relative term for a songwriter barely out of her teens) Nesbitt was already writing songs for her second album when it was released.

When we speak, she's currently halfway through recording it. It's darker than Peroxide, she says, both lyrically and "sonically", with heavier guitars and lyrics which reflect the experiences of the last year, both good and bad. "This one," says the 20-year-old Scot with the world at her feet, "is a bit more grown up."

But no songs about golf, which is probably a good thing.

Nina Nesbitt performs at the Ryder Cup Gala Concert at the SSE Hydro in Glasgow on September 24; tickets are on sale now and available from www.ticketmaster.co.uk or by calling 08444 999 990. Nina Nesbitt was photographed at the G&V Royal Mile Hotel, Edinburgh