Tostada,

I'm no expert here, but my guess is that she is mad because you aren't simply making this easy on her. She probably had a gameplan all laid out and you aren't playing by her rules. She thought this would be easy and she'd be "happier". Now she has to deal with reality. Besides if you are the bad guy, then she can justify leaving in her own mind.

Try to stay calm, for the kids if nothing else.