Is it the AFC in me that makes me feel bad for her boyfriend? Because that is the only thing holding me back from communicating with her further. Obviously if anything happens it'd just be a hook up I am not interested in "dating" her.
Is hooking up with girls that have boyfriends frowned upon in the community?

It boils down on how YOU feel about it. There was one time i can clearly recall hooking up with a girl for quite some time. Only to find out that she INDEED have a boyfriend, i felt like shit. Because i didn't know before hand that she had one, till one time while we were hooking up he called and I heard the conversation.

I felt bad for the guy, he thinks he is talking to a girl he is head over heels for... to me she was just like every other girl use and throw away... Needless to say after I figured out she had a boyfriend I immediately made an excuse to leave.

Personally I am not a fan of doing things if a girl has a boyfriend, but if she gives you her number it can't "hurt" to talk. She may leave the guy, the situation can change, etc. I know some guys on here would say "screw the guy" but as someone that believes in karma i wouldn't want the same happen to me.

Hey there, irregardless of whether is she using anyone it will all boil down to how you feel about it ,like how andd95 is explaining it.

I did hook up with a girl who had a boyfriend too but in this case i was fully aware of her situation before the hook-up.

I did feel guilty for a while but when I look back , i thought , hey nobody forced anyone to do anything , she cheated willingly , so why feel bad?