I can understand why this is especially difficult. It has abandonment plus uncertainty.

Here's how I'd feel.

If I knew T was coming home, I'd wait for her. Painful, but it would be worth it when I saw her again.

If I knew T wasn't coming home, I'd grieve and then (months later!) think about some other source of therapy. But I don't want to do that if there is any chance of T coming home, because it would be disloyal.

However, T has already said, "Don't wait for me!" She has already forgiven me in advance for making plans without her. That releases me from any promise I may have made to myself or to her. So my next step would be to grieve and then if she still wasn't home, to think about my therapy needs and how to meet them without her.