Well, it's possible that she managed to set the alarm volume to zero... (Each type of sound has its own independent volume... Unfortunately, there doesn't seem to be a way to adjust the alarm volume unless the alarm sound is playing -OR- you're at the right place in the clock app...)
Try this...
1) Open the clock app.
2) Select the Timer.
3) Tap the "Alert sound" button.
4) Click the volume rocker -up- a couple of times.
5) Tap the "Snooze" sound.
As long as you're on the alert sound selector dialog, you can adjust the alarm volume. Each time you tap the "Snooze", it should beep for about 8 seconds.
Let us know if this fixed it or not.