I've had this same issue in the past, but not from taking a prescription. A few things come to mind:
Soaking her feet/hands in parafin (such as they do in spas before a pedicure or manicure) might help.
Wetting her hands, then applying her favorite moisturizer and then covering her hands in either vinyl or latex gloves would work. Sandwich baggies work in a pinch. Do the same for her feet, and wrapping them in clear plastic wrap like saran wrap will work. Do not unwrap hands/feet for at least two hours.
Make sure that when she wears shoes, she wears shoes that offer excellent support, such as a custom shoe, high quality walking shoe (either athletic shoe or shoes that nurses might wear), or even hiking boot.
Gently exfoliate her feet with something like a loofah or pumice stone, or even very fine grained sandpaper.
Some people do very well soaking their feet or bathing in saltwater baths (just plain ol' bath salts or even Epsom salts, I think).
Wear gloves whenever she's doing dishes to keep her hands from getting wet and then repeatedly drying out.
Avoid most off the shelf lotions that have perfumes in them. The alcohol in the perfum will dry her hands out even more.
The parafin soak is supposed to feel really good, so I'd definitely try that first.
I am female, and was born in 1972 with Lamellar Ichthyosis.