What is the crowd's opinion of
Avira Mobile Security?
From 3.5 billion comments
2 reviews of this app found across the web:
Whether that program can work its way through your network is hard to guess. Though be it this virus or another, regular checking of each machine is an unfortunate part of worldly connections.
Phones are less likely to be infected, but it happens. There are malware checkers for Android, and virus checkers for iOS. Though I suspect most people run them whenever suspicious, then uninstall to save battery life.
Sounds like an issue on the phone - some spyware might be logging passwords; happens a lot through free crappy games or random "fun" apps.
Advise her to install an antivirus app; I can recommend the free Avira (both Android and iOS): https://www.avira.com/en/free-antivirus-ios (there's a link on top of the page to the Android version).
Not using apps for specific shops in the first place would be another recommendation...