Maybe try weaning yourself away little by little, if you're not ready for cold turkey? Identify the things that make you feel connected to her and stop doing those things one at a time. Distance your sessions farther apart. Reduce the time you spend with her and thinking about her. If you find yourself wanting her, redirect yourself to other activities or distractions. Replace her with something healthier for you. And when it hurts, just grieve it.

I'm not sure there's a way of leaving a painful relationship without enduring further pain, honestly. I have never attached to a therapist, but I've had to leave some terrible toxic relationships. Cold turkey has been the most effective way of ending it in my experience but it does suck. You just kind of have to acknowledge the terribleness and keep going. With my worst one, I was able to do it because I had just started graduate school and all my focus had to be on deadlines and research. It kept me going.

I'm sorry you're in this position and you deserve better. Good luck.