Yes, men are bullying female gamer.
Also women are bullying male gamer.
Thought it's important to note that it's some men and some women. Assholes will bully people for whatever reason. If you show them that they insulted you with X, they will keep doing it exactly because it insulted you. If X is your gender, then it will gender insults. If it's your sexuality, they will insult your sexuality. If it's your bad taste in video games, then you dese- wait no, ignore that. They will bully for your taste.
People are assholes, learn to deal with it. Seriously, the best thing you can do on the internet is learn to ignore people, don't trust everything you read and grow a thicker skin. I'm fighting an impossible battle with my mother who reads comments on youtube and then gets mad and depressed because "Why are people so mean?!?". She just doesn't want to understand that people write that shit just to get someone worked up, coupled with anonymity, frustration and what not, people are assholes. They can even be nice people actually, but have a bad day and write a single bad comment. When you add up the number of all people suing the internet and everyone having a bad day every now and then, there will be tons of "mean" comments.
But then again, maybe we shouldn't even be using the word bully. It's quite a stupid term when they can't actually do that. They can write bullshit, but you can ignore it. It's not even remotely similar to the oldfasioned bullying you could see back in the days in school where you would get physically and mentally assaulted and you couldn't do anything about ti because the idiotic adults would just say "eh, it's just kids being kids".
You have the mute button in games, ignore button on forums, delete them from friends on facebook (why the fuck did you even add those people in the first place?).
Also you need to talk with your GF if she's that much scared of the internet. That's some seriously deep issue and it's certainly not just bad experience from some random asshole doing asshole things on the internet.
EDIT:
Well that's the way to completely miss the topic. Good job me, nice going!
Okay, now that I read your post a 3rd time and actually realized that it's not internet bullying, yeah, your GF is getting bullied. I can't really help you with IRL bullying. One way would be reporting them to the college. The other one would be, if you can, get them out of the club. You started it so you can throw people out I assume. There is a real difference between being an asshole IRL and on the internet and calling someone a ***** for no fucking reason other than not wanting her in your club is beyond pathetic.