I don't like the way she calls it gibberish. That to me, makes them seem old to them kids or if she's white, a racist. On the other hand, I know kids at my school who have no idea how to code switch. They will use text acronyms in a formal paper like it's nothing. And I have to explain what the difference is between formal language and the language you use in texting. Yeah, that's common sense to us, but for some of them it's new.
This teacher needs to affirm the so called "gibberish" (I mean you're an English teacher and should appreciate language. Especially with the screwed up the English language is with its weird rules). And at the same time teach them about code switching which they will need in life.