I see what you mean. I think other people here have given a letter or sent an email to their T containing this kind of information, but then have taken their time in actually being able to talk about it in session. It's not like once she's read the letter you have to talk about all of that. She might help you to find a place where you could begin, and you could go slowly. But I think, given how much anxiety this is causing you, it should bring you some relief to have gotten the letter out of your hands.

Maybe instead of addressing the contents of the letter, after she reads it you could talk to her about your fears about crying in session. A lot of very caring T's do not make a big deal out of a client crying, which is no reflection on how much they care or how well they're listening or empathizing... it's just that they don't want the client to think it's a big deal, and it hardly fazes them because they see a lot of tears in their daily work. So if it would upset you if she was undemonstrative, it would be good to let her know in advance I think.