This is such a hard situation and I'm sorry you're going through It.

How do you feel you're coping generally with your life at the moment? Could that be a deciding factor whether you see another T in the meantime or wait it out? If you feel you're managing ok maybe see how you go with your pdoc's support as that could give you some insight into how you might cope long term when your T retires.

If you're not coping that well, maybe the offer to see another T at the clinic might be good to accept for now. You might take to the new T better than you think and s/he could be a valuable source of support while your T is off and perhaps longer term.

Whatever you decide, it does seem that unfortunately your T's health is very unstable at the moment and you may need to make a decision based on not knowing how long term the work with her will be. Or at least that would be my concern in your situation.