There is a product called “Liquid Bandage” which she could try. Here is the web site for it. http://band-aid.com/liquid_bandage.shtml. Has she tried pricking the blisters, then soaking her fingertips in salt water to draw them out?
She could also try dabbing her fingers in meths – methylated spirits a couple of times a day to dry out and harden her fingers. That is what I did as a kid, and it seemed to work for me.