Well, she's correct that sadly boys/men do still have it easier, certainly globally, but also in our society it's still true in lots of ways.
So her response of wanting to flee her gender is rational, from that perspective and I think should be treated as such.
However, she can't. (Nor am I suggesting I would want females to become males even if they could - I am simply saying I understand why some would wish it might be possible, given the power of the patriarchy globally).
So in your position I would talk to her about ways that brave feminists fight discrimination against women, have achieved great steps in this so far, and what more can be done.
About all the wonderful, bold women who have made a difference in the world despite the odds being stacked against them etc.
You will find lots of great age-appropriate resources for this on-line I am sure if you look.
My own daughter, only a little older, seems very surrounded by all of this ideology - it's very popular at this age among certain subsets of kids. Tho she is clear she herself is a young woman. (Whether a straight one or a bi one she's yet to decide, she says, which seems pretty valid to me and is of course an entirely different issue).
I try to listen to the genuine, potentially transformational (excuse my language - I mean transforming the world) rage that is behind much of what she says - her anger at what she knows about the way women (and other groups) have been marginalised, objectified and abused across history. And then try to help her work out how that can be chanelled constructively for good in the world, rather than turned inwards in a futile desire to escape or even eradicate ones own identity.