Sometimes powering down the iPhone waiting several seconds and then powering it up again will clear the problems. Basically a reboot, but that does not close any open apps. From your description, I would bet every app on her iPhone is open in the background and shutting down the ones she is not immediately using may help. (Double clicking on the app button will bring up a list of the open apps. Swipe each of them up toward the top the screen to quit the app.)
Rebooting the iPhone will very definitely close any running apps.
There is some confusion about the list you see when you double-tap the home button. It's frequently, and erroneously, described as giving you a list of apps that are still running in the background. What it actually shows you is a list of recent apps, whether they're still running or not.
Very few apps continue running once you shift focus away from them, whether by switching to another app or by having the screen go to sleep. When either of those events occur, the app is sent a message saying, in effect, "you've just lost the screen. Now would be a good time to save whatever you need to save so that, when you get the screen back, you can make the user believe you were running the whole time."
Usually, the app responds by saving to SSD whatever it needs to, and then waits for more news. Its code and data remain in RAM, but it's not running. It's just waiting. It may get one of the following messages next:
- You got the screen back. You may resume running.
- Some other app wants your memory. Give back what you can easily spare. (If you get a chance to run again, you'll have to rebuild/reload whatever data or code you released.)
- No message at all. The OS may just kill the app and yank all of its RAM, with no further warning. This does not remove the app from the Recent Apps list.
Pre-iOS 7, apps could continue doing limited work in the background, but they had to beg the OS for permission, and there were very few things a program could do. It could:
- Continue playing audio. (The Music and Podcasts apps, for example.)
- Continue doing telephony. (The Phone or Skype apps, for example.)
- Continue monitoring GPS. (An app that records your hiking or biking stats, for example.)
- Beg for up to 5 seconds of internet time, to finish an upload/download, but the transfer would be summarily broken off and the app terminated if the transfer wasn't complete by then.
iOS 7 relaxed the restrictions on background processing somewhat, but the fact remains: most apps do absolutely no processing and consume zero CPU or battery when they aren't frontmost. Background apps may still be using RAM, but the front app gets first dibs. If it needs more RAM, it gets it, even if the OS has to kill every other app to get it.
One thing that has always been true is that the Recent Apps list (the one you get by double-tapping home) has NEVER told you what apps are running. If you remove an app from the Recent Apps list, it immediately loses whatever RAM it was still holding, and IF it was still running, it stops, but the converse is not true. Seeing an app in the Recent Apps list does not mean it's using any RAM or any battery.
That was occasionally useful. A program recording GPS data in the background, for example, could sample location data so frequently that the radios never had a chance to turn off. Or it could do so much processing of the location data that it consumes excessive CPU. IF you have such an app running in the background, removing it from Recent Apps could be beneficial.
That's a big IF, and overlooking it led many users to believe that
every Recent App was still "running" and consuming battery and CPU. That was never true.
Another factor that led people to over-estimate how much background processing was going on was push notifications. You may see a notice on your screen that something has just happened (for example, your farm's crops are ready to harvest), and they assume that means the relevant app must be still running. Actually, what happens is that an app can register for the notification to come up on the screen when the event happens, but the app is not running in the meantime, and is not even running when you see the notification. It doesn't launch until (and if) you tap on the notification. The "event" could be based on elapsed time (when your crops are ready), or in response to a push from the app's online server. Push notifications get sent to Apple, which forwards them to the OS on the iOS device, which puts up the notification to notify the user, but does not at that time notify the app. Just because an app seems to be putting notifications on your screen does not mean the app is running or even using RAM.