Well - I think kids are smarter than what we give them credit for. Mine are, anyway.
This is a long journey, and I know you're doing your best. Sometimes I wonder what would have been different if I'd just said, "Okay," when H threatened to go get an apartment back in January. Or if he'd gone to her city to break up with her, which he threatened to do the first time I asked (he claimed he was going to drive 1000 miles so he could do it in person).
You cannot control her. You can't control what's going on in her head. It doesn't make sense, it's not rational, and anything you or your family say to her will not make her suddenly snap out of it. That is the shocking, unbelievable, crazy truth.