I know exactly what you mean, but I don't think that's the case here. A kid or anyone reading the word, say, genre, knowing what it means and how to use it, but not hearing it, thus not knowing how to pronounce it is normal. As they hear the word more, they'll begin to say it correctly or be corrected by someone else. Some of the mistakes she makes are more idiotic, than, 'I read, but am unsure of the pronunciation' or using a word where another would've been better. Even the way she puts her thoughts together, at its worse, the phrases are just dumbly combined like 'scrumption down', 'sexually strived', or in the example I listed of 'smiling with air' that's poor articulation/lack of a vocabulary to pull from. That's more than, say, pronouncing 'subtle'(suttle/suh-tul) like 'sub-tul' and saying "he wasn't very sub-tle about it', which would be used correctly in the right context, but said incorrectly from not having heard the word. That would be understandable.
While not scholars, her friends do know basic grammar and can articulate their thoughts. What gets me is, we've seen Destiny and even mild mannered Becky correct her word usage, which points to them doing it offline, with the reasoning that, if they'd do it in a vlog for the public, they're definitely doing it privately. People joke about Destiny being stupid, but her grammar is generally fine. She has the knowledge that you'd expect from someone who graduated high school, even if she looks a bit slow and acts immature. Amber may not surround herself with geniuses, but none of them, that I can think of, speak more poorly than she does. Not Eric, Rickie, or even Dana.
To be honest, stuff like,'impreciating, 'inscrutiating', talking about how to 'storage' something rather than store it, her scale not being 'liable' (rather than reliable), basic grammar mistakes like not knowing the past-tenses of common words, highered rather than raised, dogs having natural extinct, declaring she hasn't 'dranked' water, saying 'wroten' instead of written, and declaring ' I've never almost drownded" point more towards dull/dumb than anything else. That's how a 4 year old speaks, rather than a 14 year old *who might benefit from audiobooks.
* I see Becky has been located. That's an.. interesting haircut and she's lost a lot of weight.