The default on iOS is a 6-digit PIN for which you get ten attempts, with an increasing penalty after the first few. iOS really really pushes you to set a passcode. If you bypass that, then that's on you, even more so when your device contains anything you wouldn't like others to see, be it lost or stolen or submitted for service.
Assuming she didn't have something to backup the data to, then it would make some sense for her to disable the passcode so somebody could perform the repair without requiring the erasure of her data.
With iCloud Backup enabled, your device automatically backs itself up overnight when the display is off and it's connected to power and Wi-Fi; manual backups can also be triggered any time — such as just before you wipe it to send it in for service.
Apple includes these instructions in their servicing kit (the box they send you to send in your phone), and also provides them in person if you drop off the phone at a store; you are specifically asked if you have a backup.