I spent nearly a year working as a driving examiner for Queensland Transport several years ago. I never heard of anyone taking 100 lessons (between 100 - 150 hours of instruction). However, it was not uncommon to have people take five or more attempts at passing the practical driving test. My record was an African lady who finally passed her driving assessment after 13 attempts.
Nerves are a very funny thing with some people. I had clients who were barely able to hold their foot on the clutch or operate the indicators as they were shaking too much. I used to feel sorry for them as they made it impossible for me as an examiner to pass them.
Good luck to the young lady, I hope she manages to keep her nerves under control when she's in a vehicle by herself.