I think that's part of the victimization.

The sources she relies upon also say that she can't rely on anyone else. So she buys into that line, also, and therefore discounts everything not from Breitbart or Gateway Pundit out-of-hand. Sort of like "the bible is God's word because it says so right in the bible".

Sure, there is a choice made also. She can choose not to verify and stay in the bubble. But I wonder if it isn't akin to battered-wife-syndrome, where she could leave, but she doesn't because she thinks she can't.

Breitbart has low credibility:
https://mediabiasfactcheck.com/breitbart/

But they say they have "the truth", and only they do.

There are a lot of independent entities to fact-check a source. One just needs to use them. I get that it's particularly frustrating when you can fact check something in less than 10 seconds, and determine it is complete rubbish. Why didn't the person do that also? Why do they continue to rely on low-credibility sources? Humans have a history of doing that, especially when they are being told something that reinforces what they already believe.