It's "can't."
As in, her brain is turning to goo so she does not have the ability to accomplish it on a daily basis. Streaming is about the only "career" remaining, because as you said, you get fired from normal jobs when you are literally losing your mind.
The time is coming where she'll be out on the streets in a box somewhere without being able to support herself. I do not fault the crazy woman for trying to be self-sufficient until then. And the absolute stone-cold FACT of the matter is, her drinking and saying she feels like killing herself on stream did not encourage anyone else to commit self-harm, and was financially beneficial for both herself and Twitch. There are times when rules should be bent, because they do not capture every possible edge case reality can throw at them. This was one of them, and I don't feel like it's some absurd claim to say that she's been wronged or to feel bad for her.
In a perfect world she probably would be. Nobody cares about crazy people until they kill someone, however. You'll notice I never said "oh she'll end up in an asylum at some point" because most schizophrenics become homeless vagrants eventually. That's life. No one wants to pay for her supervision, no one wants to pay for her program, but they will throw pennies at the crazy woman for a laugh. I do not begrudge her trying to get pennies while she can.