Not difficult. In your sudoers, just add:
herUsername ALL=(ALL) /path/to/her/script
Then she should be able to run only that script as sudo, and not be able to run any other commands as sudo.
However, you probably want to ensure she doesn't have write access to the script (otherwise she could put 'sh' in there and get a full shell!). So you want to take a copy
of her script, make sure she can't alter the copy, and then allow her to run the copy as sudo.