I can't say I know why that has happened, or how to fix it. What I can suggest, and I can only suggest it because I've nothing else to suggest, is that you try the procedure I followed when all of a sudden I could not connect to wi-fi, and which fixed that problem:
First, double-tap the button at the bottom of the screen. That shows all of the apps presently "open" on the ipod. Then, hold your finger down on an icon for several seconds. This will cause the visible icons to wiggle. Close each individual app by pressing the red "minus" symbol on the upper-left of each icon. (This could take a while if your daughter has not ever closed any of her apps. It's allegedly a good thing to do this process periodically to help with battery life.) Finally, after you have closed all open apps, shut off the ipod, and restart.
If that works, I have no idea why.