How to Restore the Flashlight Feature on an iPhone XR?

If she’s looking in the App Store for the flashlight, that won't work since it's a native feature. It's not an app you can download. Make sure to check the control panel as mentioned in the previous answer—swiping down should help you access it right away.

I get that she might be hesitant to reset the device, especially if she thinks it will delete her stuff. A factory reset isn't necessary to get the flashlight back. Just focus on the control panel like others suggested!

The flashlight is actually a built-in feature, so you can't delete it entirely. You might just need to re-add it to the control center. Try swiping down from the top right corner of the screen to access the control panel where you see things like brightness and volume. Long press on it like you would on the Home Screen, and the icons should start wiggling. You can then try adding the flashlight back by tapping 'add control' at the bottom of the panel.