How to get over this?

Obiviously, you are not comfortable with her because of her past. That should be taken seriously because your afraid she might give you something and be messing with other guys. You should just live by yourself or a trusted friend. If you like her, you need to take things slow and if she can't handle that then you need to let her go. There is a reason why your getting that feeling that something is not right. Your twenty years old get your education out of the way then worry about relationships. Don't have if it's not comfortable for you. Listen to yourself. Don't feel obligated to do something for her.