In addition to clearing the watch history, I'd suggest making them as "Do not recommend channel" in the Home view, refresh and do the same for the next batch. This will stop the channels popping up at all. Then use it to watch a few more normal ones. Of course the algorithm will pull to the right over time, but removing channels from the recommendation rotation should slow things down.

The only thing I can really suggest is to start culling some of the worst, and introduce some counter-influences like debunkers, in hopes of her feed organically at least introducing some of that to her over time.

I am not sure if she would watch, but there is at least the possibility. Even if you kill her account in some fashion, if she just rejoins and starts looking for the same stuff again...

What if you started disliking these extremist videos, and explicitly liking more tame videos with the kind of content she would enjoy? This might tell the algorithm to prefer less polarizing videos over time.

The caveat is, I've heard likes/dislikes "don't count" unless you've watched a certain percentage of the video, at least more than a few seconds. So you can't just sit there and speed through clicking dislike on everything.

Another thing you can try is clicking algorithm-suggested videos that seem less radical than the current one. For example, on the home screen, click on something innocuous that's trending. From "related videos," in any video, pick literally anything that's not what she's already watching.

You will probably have to do this for a while, but eventually she might "latch on" to whatever the algorithm starts suggesting. She almost certainly won't stop watching those radical videos entirely - people that age are set in their ways. But maybe you can get her to watch less.

Dislike and “do not suggest” as many of such videos as you find on recommendation. Block a few channels. Like some random non aggressive channels and non political channels and videos. See if any bad channels are subscribed and unsub+block them.

So this for few days and her algos will hopefully be clean.

You can't, it's like trying to fix your mom's phone. The only way is resetting it, try resetting your mom.

Create a new YouTube profile with the same name and picture and set it as the default watch profile. Then just preload it with subscriptions from a varied amount of content and a few stray likes here and there for content she might like in general. Don’t mention what happened and just remove the old profile after a while.

I had to log into my 84-year-old grandmother's YouTube account and unsubscribe from a bunch of stuff, "Not interested" on a bunch of stuff, subscribed to more mainstream news sources... But it only works for a couple months.

The problem is the algorithm that values viewing time over anything else.

Watch a news clip from a real news source and then it recommends Fox News. Watch Fox News and then it recommends PragerU. Watch PragerU and then it recommends The Daily Wire. Watch that and then it recommends Steven Crowder. A couple years ago it would go even stupider than Crowder, she'd start getting those videos where it's computer voice talking over stock footage about Hillary Clinton being arrested for being a demonic pedophile. Luckily most of those channels are banned at this point or at least the algorithm doesn't recommend them.

I've thought about putting her into restricted mode, but I think that would be too obvious that I'm manipulating the strings in the background.

Then I thought she's 84, she's going to be dead in a few years, she doesn't vote, does it really matter that she's concerned about trans people trying to cut off little boy's penises or thinks that Obama is wearing ankle monitor because he was arrested by the Trump administration or that aliens are visiting the Earth because she heard it on Joe Rogan?