Ask your vet before you put bun on any sort of diet. Stickers is actually a good weight for her breed, but she LOOKS chunky, cause her breed is a bit stockier than some other slim buns.
Veggies – depends on WHAT veggies she’s getting. Kale is actually pretty high carb for a veggie, at 6g per 1cup. Carrot and the like are high in sugar, which can be fattening. So, for weight loss, you want to go with the low carb, low calorie veg options as much as possible and limit the ones with higher.
Unlimited grassy hay (not alfalfa blend) and cut down the pellets a little more would be my first thing to do, if I was going to try to get a bun to lose weight. Pellets are just to make up for the nutrition they don’t get in veg/hay (because most people can’t feed them the proper variety to give them everything they need) and are pretty calorie rich. If you want an 8lb rabbit to maintain weight, 1/3 cup is recommended by Oxbow.