Well, the trouble with that is this...and I've been thinking about this all morning. We share a car, so do I go ahead and tell her that if she's going to talk to him, she needs to leave and just be stuck at home with no car?
I mean, I think the problem is that she knows that I can tell her to not talk to him on the phone in our house, but I have no way of enforcing it. I can't think of a consequence that I could enforce.