Nesting/Burrowing in Litter Box?

I've recently accepted a rehomed rabbit into my care and will be moving to a new apartment in about a week. Her space definitely doesnt have enough enrichment since she just doesnt have the space she needs currently but ive recently switched her litter box to just a bin of hay and noticed that she is moving around the hay a lot. She keeps it mostly in the box, but will use her mouth to move around large clumps. She definitely digs a lot in blankets and gets picky about where they are and im just wondering if theres a certain reason for this behavior.

Shes not spayed yet, as her previous owners never took her to the vet and im waiting to let her settle in more before I take her in for surgery. She's never been around other rabbits as she tends to be agressive, so theres no risk of her being pregnant.