I'm mad that my girlfriend won't stand up to her parents
Does it make you angry that she's not standing up for herself?
Yes, she's behaving like a spoiled brat these days
It is  hard to see the people you care about being taken advantage of and wanting them to stand up for themselves. It will help your relationship to know that you are with a strong person.
She can't let go of anything. I have my limits.
Well, you should speak with her about it and what you would like for her to do. Maybe with your support and knowing what you want, she'll be more willing to stand up to their parents.