Touching you without your consent is sexual abuse, whether she's your GF or not. Doing that is disrespectful and demeaning. Please consider the possibility that you could stand up for yourself and tell her that you definitely do not want to be touched. Engaging in sex when you don't want to is soul-crushing.

I don't know if I would give her the benefit of the doubt, but people who care about their partners and don't want to retraumatize them are careful about their touching. My H can be really dense in some ways about respecting my space, but he is incredibly respectful about respecting my bodily integrity. He stops immediately if I say no and apologizes for misreading signals or what not. He would never want me to do something that I didn't want to do, and he would never want to hurt me. You deserve someone who treats you like YOU matter and you are not just a tool to get them off.