Why are you continuing with her via phone while she's away? It's understandable that her malpractice insurance won't cover her from another state, and most won't cover therapy by phone. Is she even licensed in the state where she'll be? If not, she technically shouldn't be practicing at all. So I doubt she is considering whatever arrangement she will have with you as therapy (because I don't see how she gets past the licensing issue, and I don't understand at all how she thinks she can continue to charge you, either--seems ethically slippery). Although disruptive, it may make more sense to only see someone locally for the year, and then choose (or not) to resume with her when she returns. That would help you financially, and put you in a more stable situation if life does change and she makes a decision not to return. Maybe she would be willing to continue some sort of contact for the year, but not at the level of therapy.

While it's understandable that you feel aggrieved and deserving of a fuller explanation, she has explained as much as you, as a client, are owed. You can be angry about that, but it doesn't change anything. And it's clearly not going to influence her decision. I don't think she's being honest about her practice and your work by trying to move for a year, yet keep her practice active. It seems as though having you see someone locally, too, is a way of her covering herself malpractice-wise. It really does sound unethical to me, even if it meets her obligation legally.