It does sound like the issue is with that A5 phone, with a remote possibility that your home WiFi is just marginally performing well enough your other devices are OK but your wife's A5 is having its problems. Re-locating your wireless router (be it your own separate device or a carrier-supplied modem/router) from under a desk to on top of a cabinet can help extend your effective WiFi signal range. (Signal strength has a direct correlation with resulting bandwidth speed as wireless connectivity has so many such variables). If you do have your own router and it has an external antenna (or antennas) re-aiming it can often make subtle changes in WiFi coverage, giving otherwise weak areas a better signal.
But getting back to that A5, does she have any issues using other WiFi networks or is this just a problem in your home? If the former try restarting it into its Recovery Mode (power if off and restart it while simultaneously holding down the Volume Up, the Home, and the Power buttons). Recovery Mode is a text only interface so you need to follow the indicated instructions to navigate the various menus, select the option to wipe the system cache partition. This action will only take a few seconds and then you need to restart it so it starts up back to its normal state. The system cache partition is its own dedicated partition and is completely separate from the general data partition, where all her files, settings, user installed apps, etc. are stored so wiping the system cache has no affect with her stored data. If this connectivity issue is just with your home WiFi though, try deleting your home WiFi network and re-adding it -- go to Settings >> Wi-Fi, tap on your connected network and tap on the 'Forget' button. Now re-enter your network and see if it's working better.
If there's still no change, try installing this Wifi Analyzer app from the Play Store onto that A5 and on one of your other mobile devices.
https://forums.androidcentral.com/e...s?id=com.farproc.wifi.analyzer&token=x9fWheYP
With both devices running the app do a quick walk-through of your home and note the effective range that each device is receiving. Along with giving you a basic mapping of your home's effective WiFi coverage you can get a one-to-one comparison on why your wife's A5 is having issues while your other devices are OK.
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