Is it okay to get aroused when my girlfriend tells me about her sexual assault?
Why would it turn you on?
She has great taste in sexual stuff.
You should not find pleasure in someone's violent trauma. You should seek professional help before you hurt someone.
I'm not hurting anyone. She likes it.
Your gf went through a seriously traumatic experience with her rape and you getting off on it is an incorrect use of sexual energy. Support your gf in her recovery and get help from a counselor for your own issues.