Nearly every time it takes me hours if not days to do a bunch of scans, install updates and purge whatever garbage has been installed by various malware that she's somehow managed to find. I've done more than a few clean wipes, bought her new machines and yet still she figures out how to kill it again. Most of the time it's caused by her playing some silly online puzzle game, or clicking a link in an email or some sort of fake notification... or AOL, which she refuses to ditch even though it's a huge vector.
It's been decades and she still hasn't learned how to avoid this stuff correctly. I've tried every malware scanner & notification software on the market, and each one of them is eventually bypassed by clever malware or in some cases like AVG or Norton, BECOMES the friggin problem.
Basically, my conclusion is if your parent has a problem like this the only solution is refuse to help them anymore if they insist on using Windows as their primary web device and make them get a Mac and/or an iPad, maybe a Chromebook as others suggested. Then get rid of the Windows PC or simply tell them not to use it for anything other than printing / scanning etc. There is no winning otherwise. Windows for some folks is just plain bad news