Never hand a boomer your phone. Especially an elderly boomer, and especially if that boomer is your mother. They will always start swiping. It's like their brain just deflates. Their eyes glaze over. They get this wide, tranquil smile, as if to say, "Hot dawwg! This boundless collection of photos I've been handed is going to be a real treat!", and they just start swiping. They just start fucking swiping.
I love that my gallery app has a "guest view". I can select some photos, tap "guest view" and hand someone my phone. They can then only swipe across these photos, and if they try to leave the app the lock screen comes up.
I apologize for any offense I may have caused, but I believe your presence here is no coincidence. You have to be the messenger. Please pass it along to the others via email chain letter, or perhaps more effectively, state that Mark Zuckerberg has changed the rules of Facebook and requires all users to automatically swipe when handed people's phones. That should be effective in getting Aunt Joyce to do the exact opposite.
Then they zoom out and start swiping. Just turn on Guided Access mode on iOS or Screen Pinning or App Pinning on Android. In those modes you can disable touch.