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Are the blisters on the bottom of the pads or on the area where fur is?
Are they firm, painful, and fluid discharge from the area? How long have you noticed them there?
They look like they could be papilloma viral dermal warts from the pictures (although it is difficult to get a true sense of a skin lesion without seeing it in person) They usually do not pop up as quickly as you are stating. In most cases a biopsy would be necessary to confirm a diagnosis. If the lesions are not improving or worsening - she should be reevaluated and possible have them biopsied or try a course of anti-inflammatories in conjunction with the antibiotics (keflex) to see if it helps.
Wish you the best with her and a speedy recovery. Please contact me if you have any further questions
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