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It seems she has either "corn" or "warts". Warts is the most likely diagnosis, however, a physical examination would be required to be sure.
Corns are localized thickening of the plantar skin, specially at sites of friction or weight bearing sites, and can making walking and running extremely painful.
Whereas, Warts are an infection caused by
HPV and are usually acquired by barefoot walking or sharing infected slippers.
If I was the treating doctor I would have asked her to use a topical
keratolytic preparation (salicylic acid+lactic acid liquid) to soften them up, subsequently they can be paired with a scalpel blade once a week and this can be continued for some time till the whole of the wart or corn is removed.
These can also be taken out with a cautery machine under
local anesthesia but that usually creates a wound, requiring dressing and making walking difficult, till the wound heals.
I would suggest that she visits a
dermatologist for a confirmatory diagnosis and well as the most appropriate method of treatment.
Regards