You need to send a movement key to the slave. Many people use modified movement keys {CTRL/ATL/Shift + W, A, S, D, Q, E} or the arrow keys as slave movement keys. I personally send Q and E to all my characters and I just tap one of them to strafe while I'm running my main up to pull. The slaves strafe as well and that breaks follow.

Unless you're using Jamba's Follow Strobing, in which case you need to issue a command to stop follow strobing {/jamba-follow strobeoff all}, then send a movement key to break follow.