My girlfriend might have issues... and I don't know what to do, please help?

Dude, she needs some serious help fron medical professionals and most likely drugs. If I were you I'd be running, but I realize you want to stay. She needs to know that she;s being crazy and you're not cool with that. It may hurt her feelings but it's absolutely neccesary! You said she was holding back during the violence, imagine if she didn't the next time;and yes there will be a next time and another and another... This could go bad in so many sad, destructive ways. This woman may be attractive and loving but shes also paranoid and violent. If you don't leave, this will get worse. There is not a doubt in my mind. If you must stay, advise her to seek medical help, remind her that you're trustworthy and care about her but will interact with other females platonically. If she refuses help and to accept/trust you, you absolutely must go or you will find out what she meant by "really punish you". GOOD LUCK!