Inappropriate verbal behavior (?) by a HS teacher

I wonder if she calls her girlfriends “sluts” as well. I remember seeing that on an episode of Modern Family, where Haley was speaking to one of her girlfriends affectionately in this manner. Her younger sister tried it later during an alum interview for college, thinking it made her look cool to the alum, who had seemed to be a “hip” younger woman. Predictably, it fell flat.

Regardless, it’s totally inappropriate. I’m just wondering if this is some kind of slang which is used in certain circles, which isn’t taken in a literal sense in that context. Bizarre though, that there appears to be no ability or desire to understand how awful it is, particularly in this context. And after having been told already that it is offensive, the willfully belligerent attitude about it is inexcusable.

Still shaking my head about this.