Hi MommaJulia and welcome to the forum. Aside from liability, I'm not sure what your question is. Concerning liability, yes, a portion of it falls on her if he is involved in an accident with the car.
As for the rest, she basically has two choices...well, three actually:
1. Call the authorities and report the car stolen and by whom.
2. Let the chips fall where they may and hope that he returns the car intact.
3. Take the law into her own hands and send some bigger/badder guys to get the car, which may land her in a lot of hot water depending upon how "extreme" their handling of the situation is. I don't recommend this approach at all, by the way, but am just pointing out how few options she has and, hopefully, illustrating the only one that makes real sense (i.e. #1).
In the end, your daughter is a grown woman and, unless your name is on the car's title, I'm afraid you're going to have to let her work this one out on her own.
Sorry, mama...as a mother myself, I know we want to step in and solve situations like these, but when our hands are tied, we have to learn to accept that they're adults and that they'll either make smart decisions or learn hard truths (which will hopefully make them wiser).
Just remember, this too shall pass.
