It's also the breeding ground for extremist feminism. One of my good friends stopped talking to me because of her misandry. She declared me misogynist and stopped taking to me, and I'm pretty sure she got her ideas from that site.
I'm gonna be kinda harsh here: chances are, considering the general insensitivity of boys your age, you've said some stupid shit. Don't get me wrong, as someone who's been involved in that community for a while, this is definitely its worst point (although the general genderqueer/rights community has it worse - regular trans people get called scum for not wanting their medical condition mocked), but it's because the entire movement is really shallow, with no class based analysis, no picking battles, no awareness of problems intersecting, calling everything violence, and writing off everything and everyone that's not completely perfect.
Basically, the options are, either you've said something tremendously stupid that even a 15-year-old could identify as bad, or she's just looking for brownie points for telling off boys (but if she's not a lesbian, she is also going to throw away that persona as soon as it's time to date a boy). Basically, I wouldn't worry about it either way, you have all your life to find friends you actually agree with
chances are she's going to regret it, unless she wants to surround herself with an echo chamber of people who think exactly like her (which is happening on Tumblr). People can be gross and say gross stuff you don't agree with, that's the point of being people.
for tumblrites: if you're actually familiar with the lingo and want to find some solace in writing pointing out everything that's wrong with the social justice "scene" nowadays, I'd recommend blogs like incorrectusage or recoveringsjw. Otherwise, if you want to learn something about actual feminism/other ways to make the world into a Star Trek reality, get out and read real authors.