I guess you should wait for the letter. A shame she cannot just tell you. But your first sentence says it all about how you feel about her. Maybe she wants to back off from being a disappointment to you?
Meantime, maybe you'd like to adopt
these people?
I really do understand your feeling of being used. And with your husband in poor health, perhaps it is time for your daughter and her new husband to help out or be flexible. Are you concerned that the move was to isolate her from any family intervention? Or does it appear to be a good marriage?