The fur can feel rough while one “layer” is missing. Rabbits as a rule have both wool and guard hairs and they shed them at slightly different times. If she were a different color you’d be able to easily distinguish the two types of hair with your eyes, but in an all white bun there’s no color difference between the layers. Even in an all-black bun, the wool is a blueish-grey.

Shedding in July is definitely possible, esp if it’s very warm.

Some buns molt in patches, making them look very moth-eaten for a while. It’s not an indication of poor health.

ETA: It’s good to save some of the hair you brush off. If the bun ever gets a sore hock, bunny fur is the only good material to put in a sore hock bandage.