Hi it looks like your piggy has a wound maybe abcess? And its been leeking and somehow stuck to a few strands of her fur which has sort of twirled as it dried,could be she was leaning against somthing when it began to seep, tho i dont know for sure? I hope shes going to be ok? Il be interested to know what the vets say,
I had a syrian hamster who had a abcess/ulcer on ts back and that was pretty gruesome! They gave him antibiotics,special wash and cream for him,he was very old and lasted quite some time with this,old age took him in the end,he wasnt suffering as i could see as he was eating drinking and running about,liked being picked up and also his snuggle time,he didny seem in pain otherwise i would have pts, best of luck with your little piggy i know just how worrying it is when your animal friends get poorly :/ your in my thoughts