Is it possible that the decision to demonetise or age-restrict was algorithmic, then she was too small-fry to get any interest/reconsideration from support?

We've heard loads of stories of people getting AdSense accounts shut unfairly and without recourse, for example. If that was your entire income, you already felt hard done by, and were so inclined, I could see how you might go off the rails.

For sure. Its like if your boss used an algorithm to decide your pay, and he wouldn’t disclose this algorithm to you. Some months “the algorithm” declares all your work bad and the boss pays you nothing. Meanwhile, you can see other employees’ much worse work getting paid regularly, essentially because they’re more popular and the boss likes them more. Anyone would feel unfairly treated under those circumstances, and would harbour a great deal of resentment.

Most people would leave such a “job” or try to game the algorithm, but killing the boss does also look like an obvious (if wrong and probably unproductive) option!

This just made me realize how much of a pass Youtube gets compared to Uber. Youtube expects you to provide it with content and it may arbitrarily choose to never pay you for your work. With Uber you will at least get something.

With uber you are paid when you serve a customer. Creating content, on its own, is not serving either a customer or an end user, so there can be no expectation of payment.

Well, there are at least some cases in which Youtube pays people who upload videos. When a Youtuber does get paid, who is the customer?