My son is 20yrs old. He wants his girlfriend to stay at my house where he lives with me. I don't. She has moved her stuff here and won't leave. Her family won't let her come home. All I can find out from police is that if my son is here then she can stay as his guest. How do I get her out of my house? Can't her parents be penalized for not being responsible for her?
If the police won't do anything then...Evict her. Go to the small claims courthouse by your home and file the necessary paperwork.
You didn't ask, but I'd evict your son too. He does not respect you and your rules. Let him and his "honey" find their own lovenest somewhere...other than your home! (And change your door locks and change your alarm code!)
By the way, if you evict her (or both of them) be sure to have an alarm on whenever you leave your home -- your house will be robbed within 30-90 days AFTER she (or both of them) moves out -- my prediction!