Irish,
Your XW is puzzling me. That's really strange that a mother leaves both daughters with the father and doesn't want to see them for a year. And you said that they loved each other before she moved?
Is she jealous of her daughters that they are young and lively while she is getting old and now she wants to compete with them?
What's going on in her mind?
Where did the mother instinct go?
I truly believe that she will come back soon. A mother cannot do that to her daughters for very long I believe.