The CB must not move in the same rhythm as when she passes the ball.
The CB running in must wait until the ball is in the hands of the wings, at that time she will be a natural screener or she can be played free behind the backcourt players.

The drawing is showing 2 defending backcourts.
These can also be cones.
The training restarts, after return pass between the wings and the backcourt's.
CB may also move in against the opposite defending player.
This will result in another play- and training rhythm, where the other backcourt will be the new CB.