Ok - I had these done when I was about 12 so a very long time ago
It may have changed but here goes....
It's frozen off with a blast of icey stuff. This feels ok at first then after a few hours it starts to burn then it turns into a blister and then it should fall off
For some of my warts this took once for others I had to have it done 3 or 4 times. There was one that needed doing again and I just couldn't face it
I really do think it was totally worth it but not a barrel of laughs
Hope she is ok and that the treatment goes well
You may not wish to tell her everything I have told you