Zoo, would it help to jot down some notes on what you want to tell her when she calls back? Things you forgot during session, how you feel right now, your worries and anxieties, and so on...?
I also wondered if it helped to call those other Ts in her absence. It is good sometimes to have a wider network of support and a different kind of input into one's problems and state of mind. If you can learn to trust them it will take some pressure off you and reduce anxiety and distress during her absences.

Hang in there. Best wishes,
Oceanwave