Like everything from MTG, it's a flub.

She got the phrase wrong, used it wrong, and missed the reality of the situation entirely.

It's a phrase most attributed to Oscar Wilde, but it's been around in serveral iterations for centuries. The phrase in its entirety is "Imitation is the sincerest form of flattery that mediocrity can pay to greatness."

Obviously, it's saying that copying is a compliment. And there's a lot of truth to that. It's also an admonition of sorts though, if you think about it, to be mindful of exactly what you are making "great" by copying and thus labelling yourself mediocre. Something a lot of young men following the likes of Andrew Tate and Jordan Peterson would do well to take to heart.

When you use it sarcastically, as MTG did, hurling it at someone as an invective insult, you're basically saying they have to copy you because they're not good enough, smart enough, legit enough, creative enough, whatever enough to do the thing or have come up with the thing for themselves.

MTG was telling Boebert she's mediocre.

The dis is a misfire because that's not what happened and MTG is a blithering idiot. Actually, they both are, but MTG seems to really like broadcasting it more.

Some sort of pickmeisha dis would have been far better here, except that they're two pickmeishas having a cat fight over trying to out pickmeisha the other. Disses only work well when they're unironic or not hypocritical. You need a certain level of self awareness for that; we've all seen the specimens in question so we all know there's no point in holding out hope for that.

Throw some water on them both and let's all move on.