You can’t “de-radicalize” your mom because your mom has never been “radicalized” in the first place - if she was, she’d be spray-painting ACAB on the walls and quoting Bakunin or Marx at everyone.
Your mom has been turned into a reactionary - pretty much the opposite of that which is radical. And since you have access to your mom’s youtube account, it’s radical content that is required to start levering open the cognitive dissonance that right-wing content attempts to paper over.
However, it can’t just be any radical content - it has to be radical content that specifically addresses things that are relevant to your mom. I’ll use my own mom as an example… she has always been angry about the fact that my (late) father essentially tossed away the family’s nest-egg in his obsessive attempts to become a successful business owner - I showed her some videos explaining how this neolib cult of business-ownership was popularized by the likes of Reagan and Thatcher (which she had no difficulty believing because my dad was a rabid right-winger who constantly brought these two fuckheads up in conversation during the 80s) which led to a lot of good conversations.
Obviously, your mom will not be as receptive to new information as mine is - so you may have to be a bit sneakier about it. But I don’t see too many other options for you at this point.