It is easy to be disarmed by Jay Lafferty. She's young, bubbly and perfectly amiable, yet her material is the sort of stuff that has comedy comperes pleading with her to tone down "the filth".

"I guess it has to do with the way I look," she says. "Some people don't expect me even to swear, then gasp if I say something shocking. These are just comedy views, though, the same way that there's a comedy boyfriend and a comedy family. Certainly I hope people realise that they don't actually exist - especially with all the incest gags." Appearing sweet and innocent, while delivering jokes that are Beelzebub-blue, has proved to be a winning formula for the 26-year-old, who last year got to the final of the Scottish Comedian Of The Year (SCOTY) competition. It was held at the Old Fruitmarket, a historical but cavernous venue, with a crowd of more than 500 in attendance. By some distance, this was Lafferty's biggest audience to date.

"I was on second last, which was pretty horrendous," she recalls. "It meant I had three intervals to sit through and get more worked up. Also, it was the most amount of people that I know personally who have come to see me, which brought a different kind of pressure. It's fine making an arse of yourself in front of people you don't know - they don't remind you afterwards." Despite this, she overcame her nerves to place second. The extra exposure this finish generated has lead to several bookings each week, which she now juggles with full-time work at a Dumbarton-based charity.

Though she has previously appeared at the Magners Glasgow International Comedy Festival as part of the now-defunct Don Quixote comedy troupe, her silver medal also paved the way for a 2008 solo show at Maggie May's. She is looking forward to getting back to a "real, cosy stand-up venue" and, although the crowd will be smaller than the SCOTY final, it will perhaps be her biggest achievement - especially as she is one of the youngest acts to have a solo show at this year's festival.

"I've spoken to some people much higher up the ranks than myself, and they've been surprised that I'm doing it already," she says, a little embarrassed. "I said Um, yeah, it was kind of a prize - I didn't really have much choice'. It's one of those things though: I don't know if I'd ever be ready to do one on my own if I hadn't been thrown into it. It certainly wasn't an aim for 2008 or anything."

Already in a performing minority because of her age, Lafferty is also marginalised by her sex. When asked what appearing at the festival as a girl is like, she laughs, "Well, I've never appeared as a boy". She acknowledges, though, that there aren't many female comics in the programme. Being female has occasionally been a hindrance, never more so than when dealing with promoters who only want to book men. "They don't have it as an official policy, but make it clear they'd rather have another 20-year-old guy," she says. Yet at other times, she has found it advantageous. "There are loads of guys who are good, but have so much competition that it's hard to stand out. Whereas there's only one 26-year-old female that has the style I do."

She modestly claims to have only been "working hard" at her craft since May last year, but in that short time has noticed an increase in the number of female performers in Scotland. Audiences seem to be getting more used to seeing women on the bill too. Does that mean she is safe from hecklers?

"It happens very rarely, but my act moves along pretty fast, so there isn't much room for it," she says. Lafferty adds that she, and most other female comics, usually find any hostility peculiar to women in the crowd. "Once I nearly got my head kicked in by a girl after I'd made fun of her boyfriend," she says. That may have been extreme, but she describes a typical aggressor as "a girl sitting in the front row, with a pal or boyfriend, who folds her arms the moment I walk out and puts on a face that says Aye, right. Who do you think you are?'"

Yet these sour-faced critics only serve to spur her on. "I sometimes make it my mission to make her laugh. If I succeed, then I know everyone else will be having a whale of a time."

Jay Lafferty: Offside Rules is at Maggie May's, Glasgow, on Friday