It looks like the HRS website has helped plenty!
It looks like you have a dutch rabbit, correct? Are you going by the diet regulations? Also, what type of pellets are you giving her? Timothy based should be for adults, no colored additives. Those are bad for bunny.
Not all bunnies will self regulate, in fact, if I could (but I do not) my rabbit would just eat pellets all the time, but she doesn't
She gets a tablespoon in the morning. She literally runs to me and binkies for her pellets. I treat pellets as a vitamin supplement.
What is going on in the litter box? A lot of rabbits will waste hay that is in their litter box, but it highly enourages them to eat lots of hay. I get my hay from american pet diner (via amazon) and my bunny scarfs up the hay.
Do you have any feed stores in your area? Just a warning, there maybe baby rabbits there.. so *must resist the temptation*
They tend to sell hay by the bale for really cheap. Storing it in a huge rubbermaid container helps contain the hay
My rabbit is a messy bunny as well. I put the hay in a willow basket and an empty shoe box as much as possible, but still the floor gets messy. At the end of the week, I pick up the big pieces, and use my shop vac (VERY GOOD for picking up hay!) to clean up the mess!