What on earth is she doing???

So I added sand to my tank yesterday (Carib Sea super naturals) and today my weirdo Frankie has been doing this thing where she repeatedly sticks her nose in the sand and sends up these large 'poofs'.

I'm not sure what's happening here, is she eating the sand? Digging? Or just being weird? Can someone let me know if this is normal? I'm sort of freaking out :')

For reference, this is a 29 gallon tank. She has been swimming and walking around the tank like usual, not bloated, eating worms normally. No curled gills or anything like that.

Also sorry for the bad video quality, I had to record from across the room because if I get anywhere close she stops and stares at me.