Thanks for the excellent advice
Adam and I are continuing to talk about this - Superjast really nailed some aspects of this situation that we need to keep in mind. We've moved from just not wanting to suggest anything unless and until Beth has left Caleb to now waiting till Beth has found her mental feet, so to speak. Probably we have a lot of waiting to do - right now to see what Beth's decision is about Caleb, and after that to just help her and be the best friends we can be for her. It's well worth it, either way; she's a great person that I will value as a friend even if nothing more ever comes of it.
Again, thanks for the advice - it's really helpful to get some outside perspective.