Even spayed buns can feel a bit nesty. It is after all spring. But as Sarah says, buns can mate through cage bars, and if Freyja actually is pregnant, the babies will arrive very soon now. The fur pulling occurs a day or two before the bun gives birth.
If it’s a false pregnancy it will resolve of its own. Hormones make the fur loosen from the mama bun, so when she pulls it out it’s not like she’s self-mutilating.
It looks like a lot of fur, but buns can have an almost endless amount of fur, you can brush them and brush them and collect a mountain of fur and the bun still looks like it did before you started.
Give her a nestbox. If its a false pregnancy she’ll get calmer if she can prepare for her non-babies. If she’s having babies, it’s good if she has a box to put them in so they can’t crawl away and get cold (mama buns don’t “lay” with their kits like dogs and cats do, she just goes to feed them 1-2 per day.)