Well, if she has read the letter and hasn't responded yet, then you probably don't have anything to worry about. SI is very common and so is suicidal ideation. If a T doesn't know that...well, then...I would personally start questioning them.

And if she hasn't read the letter yet, and reads it right before you see her again or when you see her again, then she'll probably give you a chance to explain anything she's concerned about.

Somethings are scary to tell other people: whether it's thoughts, feelings, or actual events. Somethings might have severe consequences attached to them, or at least we think so.

Honestly, I think you should be proud of yourself for writing the letter AND giving it to her. That takes a lot of courage in itself. And if she questions you on anything, tell her that she should be proud of you and that both things weren't easy to do. She sounds like she's a good T, so my guess is that everything will be okay