Go to settings and see if you have an option called something like "Sprint Wifi Optimizer". Turn it off if you do, it automatically tries to connect to Sprint partners like Xfinity.
Just a suggestion.
If you have an Xfinity account you can delete your device in your account setting but this might cause more problems than it fixes if she needs to do it every time she uses Xfinity wifi.
Might be Google's fault but it might be other shit messing with Google.