I'm still in therapy, so I don't know if my experience will help.

I chose to end therapy with T when T came back from maternity leave. But I had L and was already attached to her, so it made things a little easier (other things a little harder). I still have a connection with T both emotionally and contact wise. It was hard letting T go as my active therapist, but I knew it was best for me. It also helped that T has an open door policy and that she remains my backup therapist. She also allows me email contact with her once a month. I think those three things made it easier to permanently switch to L.

If you think you might be ready, why not process it in therapy before you decide to quit? And see if she will allow anything after you quit like coming back if needed or a little bit of contact.