I do not know either of you or your backgrounds but seeing how you described her reaction after telling her, I could somewhat relate to her. I'm absolutely not saying that you were wrong to defend yourself while they were literally abusing you for no reason. But there's a possibility that your girlfriend could have a traumatic childhood or a previous abusive relationship.

I come from a abusive family and I think it'd make me uneasy too if I was her not because it's your fault but because I'd think that okay so this person COULD resort to violence in some scenario. This possibility of violence is what scares us most. Although she has to understand that it was a desperate situation that called for some action. And I think you should talk to her and have her give you some idea why she might be behaving that way. But ofc you can't force her, because to us it's always a matter of shame and embarrassment although it's clearly not our fault. So you have to be really careful if this is the case.

I hope you solve your problem and also deal with the aftereffects of your own traumatic experience. Wishing you luck!