[Nancy's Hamsters]

Any itching and scratching? That's a bit near her scent gland so could be from excess licking to clean the gland or extra scent marking while awake at night too if it isn't found to be wheel rubbing.

ETA: that paper insert in your wheel shouldn't remain on there as it is just for display purposes while on the sales shelf. That would be a very likely culprit for rubbing off her fur as the edges of the thin cardboard are VERY sharp as the paper cut on my finger while removing it could attest.