I have thinking about what could I say here to help you. I you pretty hell bent on talking to her parents. You say the last thing you need is for them to hate you for not telling them that she went off the rails. I'm not sure why you think they would hate you. You cannot make her stop, nor can they. And to be politely frank with you, I'm not sure it's any of their business or yours to tell.
Last week it seemed as if you wanted this marriage to work correct? I believe that you are in shock, rightfully so. If you have any thing in your mind that wants to save this, you have to let go. Let her walk her own way. Let her tell her tell her parents. Let her live her life. Let her be.
