Snowberry
Wise Old Thumper
It's not always good to cut down pellets for ill buns- in fact I'd definately speak to a vet about what you should be feeding her.
I agree the bun should get a vet check but the amount of food the bun is getting is very excessive. I would never recommend feeding hay only as I believe buns need the vitamins in the pellets and its harder to monitor how much they are eating with hay.
I would definately cut down the pellets and cut out the museli completely.