Getting Blondie to start putting more or her foot down on the target. Thankfully I have figured out a solution to the "Where's Brita?" problem. When Blondie is having a session, Brita goes into the insulated box that I use to transport my fish. I put a soft towel on the bottom for her to rummage in. The box is light-proof and almost sound-proof, so whichever quail is inside can call all she wants and won't be heard. After 3 minutes, Blondie switches places with Brita and I can start training Brita. When they are both done they go back to their cage to eat their meal. It works great. Without the distraction of the other bird, both of them focus a lot better.
You can see Blondie start to think about pecking the target - the fact that she is offering new behaviours suggests that whatever logic a quail has is starting to kick in, and she is experimenting with new ways to try to get the food.