Hmmm... What was it that made her want to move our of her father's house?
The same things that made her mother want to leave him. I've never met him, but he has a terrible reputation.
I get the impression that she is much more of a problem for you than your girlfriend. In fact it is almost implicit that your girlfriend is enabling this behaviour.
I wouldn't say she's enabling it in the general sense of that term, it's more like she's not doing much to stop it. Remember this kid is basically a carbon copy of her father, and my girlfriend spent 20 years being dominated and psychologically abused by this guy. She's tired of fighting that fight so I think she has basically given up on her daughter.
I do speak enough French to be able to communicate effectively with the daughter, that's not a problem, it's just that my French isn't good enough for us to have long heart-to-heart talks (or knock-down-drag-out fights). The kid respects me and we have a pretty good relationship day to day; she tends to obey me more than her mother and on the few instances when I've lost my temper it had a big impression on her.
Who told her it was ok not to go to the followup appointments? Why did she have a choice in the first place?
She has rarely paid attention to rules and commandments, why would she start now? The only way to make her go would be to handcuff her and bring her there in a police car. We've tried grounding her in the past and she always goes out anyway. She's basically uncontrollable by any legal means, she's not a reasonable person.
Do I misunderstand that your original message was not a cry for help, but just a rant about something that you don't intend to take action on?
Well, I was certainly looking for advice and ideas, and a reality check. But yes, I was also venting. The fact that so many people are saying "boot her out" does make me think that this is ultimately the solution. But we're not done trying other approaches yet.