Is she new to your tank? Have you seen her eat at all?
I never had an issue with my hippo not eating, but I did with a kole tang. Turned out it just didn't like my variety of foods I offered. LOL
If I were you and she is a new addition to your tank I would suggest calling and trying whatever they were feeding her where you purchased her. I had a kole tang that would only eat these cruddy pellets the LFS
used, which I did not use, after offering her the pellets she ate readily and eventually tried other foods, once accepting them and I did away with the pellets altogether.
Is she being bullied away from the food by the clowns?
Also, perhaps if she is new she needs adjusting time as well.