Good for you! I think what you did was a huge step. It took bravery and strength to read that letter out loud and I don't know if many people could do something like that. I'm happy to hear that your therapist was so supportive.
It is natural for you to feel a lot of the pain and hurt you experienced with your attacker come back. You just opened a door and let out some of those deep hurtful feelings. It is very therapeutic to do what you did, but also scary.
You can work through this until you see your therapist again. It takes some work on your cognitive processes by changing how you think about this, but it is very possible.
One, you are not a victim. You are a survivor. It is very important that you remind yourself of this as much as you need to.
Two, you are safe and you have people who care about you
Three, you are recovering from what happened every day. You are getting better, which means you have the strength not only to survive, but to thrive.
Four, spend some time with people in your life that you feel safe with. Pamper yourself and treat yourself well. Get extra sleep, eat well, and try to laugh.
Five, allow yourself to feel. You are going through a difficult time but these feelings are good for you. You are experiencing them in a safe place and with support. It is ok to feel hurt, upset, tearful and anger. Any emotions, as long as they are not self destructive, are good feelings.
You are doing so well. You have great motivation to work through this and if you have that, you will get better.