I'm in the same boat as you, my last session is next week. I'm not considering a note or gift or anything (that's just me though, I think it's cool that you're doing that) but I wish there were some way to stay in touch with her. I've never emailed or called her before, I don't have any way to contact her. Ideally I would be her friend on facebook but I'm afraid to ask and get rejected so I probably just won't.
hang in there, I know it hurts to lose a T.