She was supposed to rearrange her practice schedule two years in advance on a prospect of one client possibly getting a new job? I guess I am not understanding this scenario. I understand you are upset, but I'm not certain she could have realistically done much differently. If you knew two years ago you needed this change, why didn't you ask for the change two years ago? I'm assuming it was because it wouldn't have worked with your schedule up until now. Likewise, it probably wouldn't have worked with hers.

Try not to shoot yourself in the foot by cancelling an appointment that you might need out of anger. Go. Talk things through. Work this out.

ETA: After I posted, saw you decided to go. Good decision.