Log in as her on your device. Delete the history, turn off ad personalisation, unsubscribe and block dodgy stuff, like and subscribe healthier things, and this is the important part: keep coming back regularly to tell YouTube you don't like any suggested videos that are down the qanon path/remove dodgy watched videos from her history.
Also, subscribe and interact with things she'll like - cute pets, crafts, knitting, whatever she's likely to watch more of. You can't just block and report, you've gotta retrain the algorithm.
It occurs to me that Kutcher and co might not have had access to the court proceedings, testimony, and evidence, but might have had a lot of access to Masterton's side of the story.
It also occurs to me that being friends with people is complicated and that bad people emotionally loan shark a lot - maybe they felt obligated to send letters of support because they were being guilt tripped about all he'd done for them or because they think being a good friend is supporting no matter what (aka being an enabler).
All that said, Kutcher's a grown up adult who should have been able to predict that supporting a sex abuser is going to conflict with being involved in an anti-sex abuse organization.