This is usually always due to an allergy. To food, environment or something she breathing.
Since it's mainly on her lower extremities I highly suspect it's a contact allergy. Start there anyway. Use a ofor free or paper litter, clean with only vinegar and water. As pure as possible laundry detergent NO chemical softness or sheets, use dryer balls.
Have u changed furniture or carpets recently? Anythg she walks on or comes into contact with is very likely the cause.
Could also be sents like I mentioned, stop all room freshners, scented candles, hair sprays....anythg wth a scent
As a last resort we can do an elimination dietary change, especially foods with chicken. Use canned foods only, much less preservatives and chemicals
Keep us posted...
Sorry for all the typos....laying down wth my iPad an get clumsy....not ofer free products ODOR free, not softness should read softners
This could be caused by any soert of skin disorder. Time to see the vet.