Suggest something to help retrain a barrel horse to stop anticipating and make better pockets.

I have a teenage girl riding a teenage horse she has partnered with for a few years that always anticipates the patterns and needs work on making proper pockets. She's great at keyhole because she can turn on a dime, but the girl doesn't have formal training and the mare is obedient, but needs someone that knows why they are doing what they're doing when they ride.

I cannot be present every time she rides so I need something to send to her as guidance. She will have others available to help her decipher meanings.

I personally would like something that also talks about proper Western Pleasure riding mechanics that she can translate to barrels, polebending, etc. because the horse does both.