Cavi,
I'm sorry you're going through this. I also have BPD and am very attached to my T of 2 years. I KNOW intellectually that it is unethical for Ts and clients to be friends, but just at my last session I asked my T why not, because part of me wishes very much that we could be friends.

She said that we wouldn't have met if I hadn't come for therapy. She said she never does therapy with her friends. It just wouldn't work. I know that's true for the reasons others have posted. I'm glad you're starting to see it too.

I don't know why your T is telling you that it's possible. She's not helping you by encouraging this friendship, and is being unethical too. Usually it's the T who keeps this boundary and the client who wants to cross it, not the other way around. I'm sorry but I have to agree that you may need to find another T. I'm also wondering what is this friendship like?