Ok, the WAS is hurting. The way I have best seen this explained is that they only see one option (D) b/c the pain of staying is greater than the pain of leaving. So, they do have pain, but to them, the remedy is to leave what they perceive is the source of that pain - the M.
As far as why your W acted like all was well, then did an about face, I don't know. Maybe to gain an advantage in the D from a legal standpoint. Maybe she was lonely. Who knows.
