Losing my therapist soon

So earlier today I had therapy, and my therapist told me at the end of the month she is no longer going to be working at the hospital I go to and is no longer going to work as a therapist, and is going to start working in a child study team at the local elementary and middle school. (I am going into high school btw)

I was definitely devastated to hear this, I had only started therapy 9 months ago and I easily clicked with her, I have gotten a lot of help from her and learned things that I hadn't figured out before (ex: I found out I had aspergers after years of not knowing and confusion) etc.

My therapist had told me she knows a lady at the high school I am going to that had worked as a therapist for many years and keeps in regular contact with that I could see once September comes and that would be my replacement, but I'm extremely upset about this. Luckily I can have about 3 more sessions with her until I truly have to say goodbye but I'm already beginning to miss her. I don't want her to go, I don't want to start over with someone else. How do I deal with this and how do I spend the next few sessions? And how did you spend your last session with a therapist? (Plus I am thinking about giving a thank you letter to her but I'm not sure if I should?) Any help/advice is appreciated.

Wow, that is really short notice. I'm sorry this happened to you. I would definitely let your T know how upset you are about the entire situation.

Losing therapists sucks. I'm sorry you have to go through this. I just had mine switch careers on me a month ago, so I can really relate.
You can most certainly give her a letter if you want. I think goodbyes are really important. We worked on our goodbye for the entire month before she left. The last session was a wrap-up of progress made, what I still wanted out of therapy, and answering some last minute questions I had. Then we did our goodbyes. It was a sad and difficult month for me, but I'm really bad with loss, and this one came right at the same time of some crazy anniversaries.
Switching can be hard, but it's good to talk about it. I know I spent a lot of time talking about what it meant to me and what it felt like. The starting over is difficult too, but my old t called my new t's agency and gave some helpful info.
I'm glad your t has someone in mind for you to see. That's always helpful. I hope you guys can wrap up effectively, and that things work out with the new t. (Hugs).

Sorry that is happening to you, I know that it can be hard.