I'm female and I'm not a hardcore feminist.
I like metal for the music. I honestly couldn't care less if it's masculine and I wouldn't say that some sub-genres of metal, such as power metal, are overly masculine anyway. I honestly do not care if men who are into metal think they are better than me because I'm female, because that's their own opinion, just like my opinion is that everyone is equal. Everyone's entitled to think what they want.
I get told that I should dress, act and be more feminine all the time and that the music I listen to isn't very 'lady like' ect. But, even before I listened to metal I wasn't very feminine. I think the majority of females who listen to metal have been somewhat 'tomboy'-ish when they were younger, but doesn't mean that all are 'hardcore feminists'.
Like it matters what's considered 'feminine' or 'masculine' anyway. I think what matters more is the music. Some people like it and some people don't, regardless of gender. I do think that a lot of females who are into alternative music lean more towards the deathcore/metalcore side of things and I'm sure a lot of you can see why as it's probably the same reason why many females were attracted to glam metal in the 80s/90s and even now.
I am pretty sure there are less females who are into metal as I have not once been to a metal concert/festival where there were more females than males, and I'm sure a lot of you will say the same. But why does this matter? Just because someone is of a different gender, it doesn't mean they aren't and can't be part of the metal 'brotherhood'. I think it's what's in your mind, how you think, not what's in your pants.