Serious. Married to the job. Nicola Sturgeon is used to hearing herself described in such terms, but there has always been a mismatch between that media image and the sparky, personable reality described by her friends and colleagues. When I meet the Deputy First Minister in her Holyrood office, she is businesslike and polished, of course - you don't spend as long as Sturgeon has in the public eye and keep the rough edges - but she is also thoughtful, considered and frank.

Sturgeon does work an awful lot, there's no getting away from that. She is on the airwaves and in the papers campaigning every day, as well as fulfilling her ministerial duties, and says she cannot remember the last day when she did not at least deal with a slew of emails and media requests.

But though she does so willingly, she still admits she sometimes wishes she could opt out. "There are days in my job, just as everybody has in their job, when you want to pull the duvet over your head in the morning and you just think, 'Oh God, I wish I did something else'. Of course you have those days; you wouldn't be human if you didn't," she says, in characteristically matter-of-fact style. "But I love doing what I do; it's the kind of job, if you ever get to the point where you don't really enjoy it, you should stop doing it because the downsides would then become intolerable."

That moment looks like being some way off. With the referendum campaign nearing its climax, Sturgeon insists that, odd as it may sound, she is enjoying it. There is no respite in sight for her: if Yes manage to close that stubborn gap in the polls and overtake No, then there will be a huge workload in terms of negotiating Scotland's extrication from the UK. If voters opt to stay in the UK, then as well as commiserations and recriminations, there will be at least 18 more months in office to contemplate.

One of the big challenges the Yes campaign faces is winning over more female voters. The polls have shown clearly that women are more likely to be undecided and more likely to vote No, than men. Sturgeon has made clear that winning their support could be the key to winning independence. So why has the campaign struggled to convince them so far?

She is instantly on her guard about overgeneralising, and acknowledges that no-one really knows for certain why women are less inclined to independence, but will venture her impression that "women take the time to think about things in a very careful and considered way", hastily adding, "which is not to say men don't".

"I also think that for women, the issues at stake in the referendum that are important to them are more likely to be issues about what the impact is on their life, their family's life, community's life."

As one would expect, she says she believes Yes can close the gap. But how?

The latest bid involves the claim by the SNP, rejected by the other main parties, that Scottish NHS funding is threatened by remaining in the UK. A recent Panelbase survey, commissioned by Yes Scotland, suggested that this could be the decisive factor in winning over female voters. But there have been other initiatives.When the SNP Government's white paper on independence was published last November, it included a high-profile "transformational" plan to provide, in stages, free childcare equivalent to primary school hours for all children aged one to five, which was apparently an attempt to woo female voters. It has been paraded many times since, including by Sturgeon, at events aimed at women.

But given that there is little evidence women are swayed on big questions such as Scottish independence by single issues such as childcare, the drive to appeal to women always ran the risk of being interpreted, at least by some women, as patronising.

Sturgeon rejects the idea that anyone would see it as patronising, adding that the policy will be of particular benefit to women, but not exclusively so. She insists it is an example of what Scotland could do with independence.

Sturgeon's very high profile in the campaign has been seen as an overture to women, but she herself does not believe that females will always be inclined to vote for others of their gender. "I think women warm to people they think are honest and sincere and doing what they believe, whether they are women or men."

Sturgeon, 44, finds herself as the face of the SNP at a time when two other Scottish parties are also led by women, Labour by Johann Lamont and the Conservatives by Ruth Davidson. Sometimes it is claimed that women are less combative in their approach to politics than men, but there was little sign of that when STV's Scotland Tonight staged a debate between Sturgeon and Lamont in February. After a section in which the two politicians were questioned by host Rona Dougall, they were, perhaps unwisely, given free range to interrogate each other, with minimal mediation. The programme became almost unwatchable as the two constantly interrupted and talked over each other. Voters seeking enlightenment would have learned very little.

"We have talked about it between ourselves and I think both of us would choose to do that differently," says Sturgeon, looking back on the broadcast, but then sidesteps into the observation that in the media and on social media, with some honourable exceptions, an impression is given of "a nasty, divisive debate", while in Scotland's communities the debate has "a completely different vibe and feel" and is very positive. This comes close to sounding as if she is blaming the media (when clearly politicians are more than capable of pitching into conflict without prompting by journalists), but she stresses that is not what she intends.

That televised debate did not do either politician many favours, but perhaps even more notable than the ill-tempered exchanges themselves, were some of the overtly sexist comments afterwards. Terms like "cat fight" and "shrill" were used, with depressing predictability. Sturgeon has had more than her fair share of such epithets in the past - how she must roll her eyes at being described as a "nippy sweetie". How much, honestly, does it annoy her?

"I probably am the wrong person to ask because I guess I get more angry about it when I see it directed against other women," she says. "I have become personally a bit inured to it over the years. You try not to allow yourself to get too drawn into that because some of the comments you see or hear or read about are very personal in terms of how you look and what you wear and the rest of it, so it's maybe a bit of a personal defence mechanism.

"It tends to be when I read that sort of thing about other women that I get most angry. So much of it is downright sexist and nasty. It's terminology that wouldn't be used about a man. Going back to the debate Johann and I had, which I don't think either of us are trying to defend: if that had been a debate between two men, it wouldn't have caused those comments. Maybe it's because people expect more when it's women and maybe we should embrace that positively."

Maybe, but that's not equality.

Sturgeon has an eight-year-old niece, who has so far shown no desire to get into politics. But if she did, her aunt would not want her to have to put up with such treatment. "We've all got an obligation to make politics something that people aspire to do for all the right reasons and that women don't feel that they've got a whole extra set of issues to contemplate before thinking that it's something for them."

She says that when she first came into politics, the pressure then, though she was not necessarily conscious of it at the time, was "to conform to the male model of doing politics ... to go along with the adversarial element of it".

"That that's how you are conditioned to be. But then you get criticised because you're not being female enough. But if you then become all female about it, you get criticised for not being serious enough. So you are kind of caught in the middle.

"When a guy would be getting called assertive, you are getting called aggressive. If Johann and I had burst into tears in that debate, not that we would have done, but if we'd shown any sign of weakness, we'd have been hammered much more than a man would have been for that as well. So what do I hope for? That women can just be themselves."

There are a greater proportion of women at Holyrood than at Westminster, but the Scottish Parliament has nevertheless developed a more confrontational style of politics than some of its architects had hoped for.

Sturgeon notes that while politics will always have an adversarial element to it, Holyrood is much more given to collaborative work and sensible debate than television viewers who only see First Minister's Questions, might think.

She has been there for 15 years, and is currently MSP for Glasgow Southside (she lives in the city with her husband, SNP chief executive Peter Murrell). So does she have friendships with people in other parties?

"There are people in all of the other parties that I like and respect and get on with very well with." She is hesitant about naming names, but gamely offers that "I like people like Kez Dugdale on the Labour benches, I think Willie Rennie's a decent guy that I get on fine with, Mary Scanlon on the Tory benches - she and I had a history when I was health secretary and she opposition health. So yeah, I like people in all of the parties."

She does not want to see Lamont or Davidson become First Minister, but thinks it "really positive" to see prominent women on both sides of the campaign. There is the future to consider and "that can only be good for younger women".