Yes to many teenagers and young 20-somethings preferring the feminine / arty / non-comforming / whatever the current label for gentler, more thoughtful, (supposedly) emotionally-competent males is. (And many of us continue to prefer some of those characteristics in later life too!)
My experience is that, while less laddish and blokey, those young men are generally no less selfish, or any more emotionally competent, at core, than your average blokey bloke. They might respect women a bit more and will be less overtly sexist but that doesn't cancel out the pursuit of self-interest. (And some use their emotional literacy and insight into women as people, to manipulate women, often quite successfully).
Also, there's a very real phenomenon of 'lesbian at college' i.e. university, where young women opt for the female end of their bisexuality (or whatever), at a time of life when the majority of young men around them seem immature, undesirable and annoying. Many of these 'lesbians' turn into apparently happily heterosexual older adults.
So I'd treat this as just another 'ooh aren't we special and didn't our generation invent sex!' bit of youthful self-absorption and experimentation and as no more or less inherently risky or difficult than any other teenage relationship.
Age gaps are always a real concern with teenagers, with so little life experience. Are you saying she's 17 and he's 19 though? That's not a big gap. Not like a 23 year-old with a 17 year-old would be.
I would counsel her against feeling the need to define herself publicly at such a young age. I'd reassure her that, as above, most people experiment a bit with early relationships, as a way of finding out who and what they really are and really want. That's all fine. Some women choose to describe themselves as lesbians for political reasons, or reasons of convenience / self-defence / short-term self-interest - and always have, it's nothing new or special. Actually recognising that you are gay (or straight, or whatever) though is something that comes from within. There's no need to declare your hand early and much to be gained by keeping things vague and allowing other people to make assumptions, until you're absolutely sure and confident about how you want to live and present yourself to the world.