I think the finer points of what is considered ethical--and certainly what is considered good practice--vary by jurisdiction, therapeutic modality and individual therapist. I agree with you that this doesn't sound like a good set up and it would make me uneasy.

But as Stopdog points out this really is a MYOB situation. It doesn't affect you directly. So, unless your friend asked your opinion (in which case tread carefully), or you have good reason to believe she is being abused (in which case say something once and then shut up and remain a safe harbor for her), you should just be happy that this is not your problem.