Well, I think Sandi is likely right about the reasons for the behavior (unfortunately) but I will state my opinion again that things need to wait until the dog sitch is wrapped up. It will be a difficult few days. Is it possible she will use that as emotional manipulation? Yes. But, I am thinking of you GW, and your girls.
A thought about the debate on whether to set a boundary or not... there is an interesting thread on the extramarital affairs forum called the "Ghandi approach". This is posted by some of the men who have made some decisions about how to confront these behaviors in their WAW's.
I have not been around as long as Sandi, I have never been a WAW, and I really only have my own sitch to go on, but I lean towards Lotus' advice and worry that you will push her farther and deeper into the A if you come accross as "controlling". There is a way to be asserive, firm, and have boundaries without making it sound like you are her father.
Don't want to make things more confusing for you, though GW. AGain, take time to grieve your dog and take care of yourself and your girls right now. ((GW))