Wait up-- help me sort out my lingo. Isn't this Mikoto being yandere, because her actions are on account of the Takase she likes and her suspicion that Rin might be a love rival? Or, do you call her yangire because the victim of her "snap" is Rin and not Takase? But yanderes are able to "snap" on people they perceive to be threatening "their love" or the person they "love", and they would still be considered "yandere"... right?
You may think I'm overthinking this. Really, I'm genuinely curious about your thoughts, and I'm also conscious about how otaku language and concepts shift and get flanderized. The general conception of "yandere" used to have an obvious horror component-- now it feels like the horror aspect ends up truncated, or built into the romantic/sexual aspect of the trope in a way where it's overpowered by the romantic/sexual aspect. Like, it just ends up averaging out to "initially sweet, but flirt with another girl and she'll break through your bedroom window at night to... turn you into a human pogo stick against your will... initially against your will".
Not that I'm accusing you of that, though-- the fact that you even knew the term "yangire" tells me you know a thing or two.