@Doctortrombone,

Unfortunately, this is a result of the background usage on the phone. As soon as the phone is giving an internet connection, the apps and device will start communicating with the network to see if there are any updates or notifications that need to go through. You can try and prevent this by turning off background app refresh on her phone, however this could be an inconvenience for some other apps.

I would recommend looking into ways to set a schedule for either the phone's Airplane Mode, or to turn off the wifi, that way when she needs to use the network, all she has to do is toggle the wifi switch.