Quick round pen session with Z

We're developing a backwards circle and I had 20 mins to spare so took Miss Z into the round pen. She can go about 1/3 of the pen circle now. She sometimes wants to turn around and I'm trying to figure out the best way to discourage that behavior and keep her moving zone 5 first. I realized at one point that I was asking her to do too much of the circle (about 1/2 the circle) and I took it down a notch to about 1/3. She was successful there. We'll keep building! I realize that having a horse this developed means we can do cool things in a short period of time. Want to keep developing her and doing more things that help her be braver, smarter and more athletic!