You sure you can go out for a walk with your T? Some Ts will do this. You can also tell your T that you would like to talk to her about something, but you're worried about having a panic attack. Ask her how she could help you cope if you did have a panic attack. And you could always ask for a break if you need one.

My T has me do deep breathing, she helps by trying to engage me in a different topic, she took me to here window and had me be mindful of everything outside, and she touches me (though I know you mentioned that wouldn't be a good thing for you). I think my T would be willing to walk with me outside. She made a comment about it once.