I'm sorry it's happened again. It can be so hard to hear, especially when the consequences of hearing that triggers old wounds.
I'm glad she admited it though... It sucks a lot to go through rupture after rupture just to find that you and T should have parted ways long ago. :/
I know you had said you think Monday will be it, but can T carry you through until you find a new T? That way you guys can terminate and she can support you in the search... just a thought.
All the questions I ask in first session tend to be specific to my issues (ex: how do they handle self-harm & chronic suicidal ideation, how available are they, what are the specific bounds of confidentiality arund sh & si... that kind of stuff). It might be beneficial to mention that you have switched T's often because their expertise was not sufficient, but maybe if you can get a better idea from T what prompted her decision, you could ask specifically how they feel they could work with a client who presents as "x"...?
Good luck in your search. Switching T's is always so hard.