based on the OP’s screen name, i don’t think she/he was trying to be a yentah, etc. It seems that as a shadchan s/he was wondering out loud if there are signs or whatnot to look out for while dating.
keeping far away from the topic of this particular couple, i can only imagine the pain of either a terrible marriage that causes one spouse to go off, or the terrible pain of a marriage that breaks up because one spouse no longer wants to be frum.