I think you're doing the right thing by distancing yourself from this girl.

Sadly, your son is going to have to learn the hard way. That may mean jail, bankruptcy, or possibly an incurable STD. First love is hard to get over, especially when it's your first everything. Sadly he doesn't know that this isn't love. He's being used. This girl may have a personality disorder. He may be codependent. It sounds like a huge mess.