What's her history? Spayed? How long? Is she trying to build a nest at all? Any changes in diet, or has her hay changed in the last month(type, texture, etc)? Any signs of dandruff, flea dirt, or skin irritation? Any environmental changes, changes in her life or routine? Does the fur look barbered(chewed), or does it look bald and plucked? Any other changes of behavior or signs of health issues?
Abby was spayed in April. No changes in diet or hay. No signs of dandruff, flea dirt, or skin irritation. Was treated with Bravecto (good for 3 months) a month ago. No changes in her environment or daily routine. Her hair looks barbered, not plucked. It has been hotter outside so iput her and Dutchess outside earlier, and bring them inside when the temp reaches 85. They have hay, veggies, and shade in their outdoor cages, separate because they are still not ye t bonded (Abby chases Dutchess,who is still scared of her).
There can be a variety of reasons for a rabbit that is barbering. Hormones, sexual frustration, boredom, stress(eg. predators, stressful environment, environmental temperatures), nutrient deficiencies(not enough protein, not enough fiber, mineral deficiencies), skin irritation(mites, fleas, allergies, fungal, etc), pain from something internal - particularly if happening only in one spot(eg. arthritis, chest pain, etc), genetic, etc. If your two rabbits aren't kept together so it can't be the other rabbit doing the barbering or couldn't be doing it through adjoining pen bars; and it's your bun doing it to herself; it could be stress related, maybe due to the heat, or possibly still hormonal related, though this is usually more plucking and not barbering.
The one time I had barbering with a spayed rabbit, was due to a different batch of hay being a stalkier hay. My rabbit liked it so much that she ate more of the hay and not enough of her pellets. The hay was too low in protein, and she wasn't eating enough pellets to balance the low protein hay, so it created a nutrient deficiency in her diet. She was barbering due to not enough protein in her diet. Which was fixed by changing to a leafier hay(higher protein) and her eating pellets again.
So you'll need to examine every aspect of your rabbits life and environment, to see if there is a possible cause you can determine, or a possible trigger for the behavior. And if it starts creating a health concern, consult with your vet right away.