How long is she in? Unless it's over 8 hours, the majority of her time in the stall should be in the dark. She should snooze and not walk the stall.
We prep stalls (feed, shavings, water), bring the horses in and then lights out. They eat and go to sleep. In between 9 -10 p.m. And out at 5/5:30 a.m. We want the horses to see the stalls as a place to rest. Not view them as punishment.