How about apologizing for how you acted when you found out ...
and then asking her if she could let you know when she has other plans so that you have enough time to make plans yourself.
That might get her to give you the "HUH?" face.
You might read up on some of the MLC advice. The WAS running back to the OP is somewhat normal, and from what I understand, you have to stay out of the way. You can't let it bother you. If you appear insecure, it could drive her back to him permanently. The WAS should only temporarily retreat and then will gradually come back closer to you. Remember patience.
This is the rough part. I've heard that the separation is a cakewalk compared to reconciling.
Good Luck... but give the MLC board a look, there's some good advice over there.
