Eek! I don't know much about chemical perms, but please
do not do a straight perm to fix the curly perm. The chemical damage will be brutal and I just don't think it'll be worth it if your girl still wants to have hair on her head.
I don't know what she can do to relax the curl, but I suggest she baby the hair with moisture and protein treatments. Check out this website for some tips: Live Curly Live Free - Curly Hair Basics