Usually the mom scratches the ground and picks up bits of food to show the chicks how to eat. Sounds like she is trying to do that.
If your brooder is big enough, you could push all the shavings to one side and sprinkle some chickstarter on the bare floor of the brooder, if it isnt too slippery for the chicks.
You could also switch from shavings to straw or even hay for bedding.
Ive always just kept mine on shavings. They figure out pretty quickly that it isnt food.
chel