Oh, iluvpups, that's hard :-) I did that but loved my T, she was just away a long time so I got an online T and worked on a wholly different "area" that the new T would have been better at than my T. However, when my T came back, I then had two T's and the embarrassment of not knowing how to handle it. I wanted to stop with the new T but it seemed so hard. I was able to tell my actual T what was going on and she explained that one T is all one can work with because of the "divided" loyalties; you end up not being "there" for either of them and can get yourself in a lot of difficulties with nowhere to turn (like you are experiencing now sort of).
I would have a frank discussion with your old T about how you feel you are getting nowhere and see if you all can understand that better; whether it's "you" or the therapy, her style, or just what it is and I'd share with her your predicament and what you'd like to try. My T was very firm that she would not work with me if I was also working with the other T, I had to choose what I wanted to do. Unfortunately, there's no "help" while you're dangling over that chasm, your legs slowly doing the splits and you try to keep one on each side

You have to grab one person's hand or the other.
I, personally, would find the "getting nowhere in my therapy" a challenge and stay with the therapist I had been working with. I don't think the therapist is as much of the equation as we are in our therapy, but I don't know how many therapists you've had before or what you're working on, etc. I was surprised that you have started with someone else but don't know if she's any better for you than who you have had.