I'm going to break up with my girlfriend because she stopped hanging out with her friends.
Why do you care if she hangs with her friends or not?
She is restless and hostile if she doesn't see her friends.
If your girlfriend is abusive toward you, then you need to end the relationship. However, if she is not being abusive, then you should not try to control who she hangs out with. If she doesn't want to see her friends, you shouldn't try to force her to since she will resent you for it.
Ok fine, I won't end the relationship.
I'm glad you've thought about it more and aren't going to end your relationship with her.