CC, yes they are... the problem is that her visa will not be renewed if she is no longer married to the turd. so, she will have to return home.
to the OP, what visa does the daughter have? i'm guessing a dependent, if they are not chinese... which means that the daughter is also dependent on the turd.
the mother will have to get permission to leave hong kong with the girl. if the father refuses, then the mother has no choice but to leave the girl here (unless they are able to work custody and residence issues out during the divorce proceedings) with her abusive father. not a great alternative for them.