I suspect she might be seeing your perfectionist tendencies above everything else, and therefore (wrongly) interpreting something as performance anxiety when perhaps it's actually a need to connect with her, to feel like she cares about you, to hear that she wants to keep working with you and feels good about working with you... something along those lines.

Sometimes (I'm speaking from experience here) perfectionists convince others that they are strong and independent and invincible and don't need anything (except maybe acknowledgement for their hard work?). I'm surprised a T would be fooled by this, though. It might be time for a new T. Or if not, then you might have to let her see some of your vulnerability by talking openly about your worries about your relationship with her. (Apologies if I am off base and reading too much of myself into your situation. )