I think I would make myself a symbol; a red flag or hankerchief, and when I got stuck, wave it or put it on my head so it covered my face (a piece of black cloth?).

My parents had agreed-upon hand signals for when my father was telling a joke to the same people the 4,000th time, LOL. It could be something you and T could agree upon together. Do you have a small stuffed animal or something you feel good with? Could you toss it to T so she could "rescue" it from your silence or stuckness? It could be a messenger or secret agent that has to get to T to let her know you're stuck. . .

I find symbols easier for me to work with than the "real" thing. Maybe just agree to talk about the weather when you get stuck? Tell T you'll try to get yourself going with "Nice day today, isn't it?" and she can help you work back into a more personal conversation. It can help you "back up" away from the scary pit/swamp so you can find the road again.