Is she dancing barefoot or with shoes?
Although it will be one of the more painful experiences of her life for about 30 seconds, a liquid-bandage product (like New-skin) will help seal the skin and create a protective layer over the area. It comes in brush on and spray. It stings pretty bad on raw skin for a few seconds, but works pretty well, and still lets the skin breath so it can heal. I used it for years as a dancer with pretty good results.
If she is wearing shoes, there is a type of sports tape that is padded but only sticks to itself (I can't remember the name) that she could wrap around that part of her foot, and then put her shoes on. It shouldn't stick to the skin, so she would probably be able to tolerate it.
Hope this helps! (Ouch!!)