You could try Teamviewer which can work on some phones but I've no idea if it will work for Android TV.

Nope. You could start Chromecast content and mirror the screen accessing a local phone or tablet.

Local = in your home Wi-Fi, e.g. install a remote "desktop" app on your wife's phone.

Time for Wifey to get a 2.0 upgrade..?

When I met my lady, her flip phone was pitched/upgraded & she was trained in using 'all things tech' accordingly.

I couldn't even imagine living with a 'Tech Civilian' let alone being with one.. I deal with enough of them servicing their devices as it is, NTY!

If she can't figure out a d-pad and 3 buttons, then how does she even manage to turn your TV on? A cable box remote has about 20 times the amount of buttons on it.