try watching and when she does it,schold her very sternly with a harsh NO! NO!.
if you can't catch her,the next morning get the pot,hose or what ever and hold it to her face and then schold her.
try this every time she does it. don't do it once a week , but every time.
let her know it's not OK with you.this will take some time,a few weeks most likely.

I had a problem with my pup digging holes after mole crickets. it took a while,but he stopped.