My depiction of sumire is a jealous, competitive, meddlesome, flirty girl that likes to toy with sarada's head, because she's competition and a threat.
In reality, a girl like that is gonna lose...knows that the one she feels she's competing with has the advantage, so she has to act extra flirty and appealing to win the affection of the boy she has a crush on. She messes with the other girls head, convincing her she's not good enough, when really, it is her that's not good enough. It's admitting defeat using reverse psychology.(Yes, I know, all of this hasn't happened, but it's what I got from the spoiler pics, "competition") Kind of like Ino and Sakura.
All that flirtiness, blinking of the eyes, the "cutesy-tootsy" act...it's an inferiority complex.Trying too hard. You're gonna lose.A man would HAVE to call bluff on a girl that knows she's gonna lose.
So, I'd go with Sarada based off of that. But, this is a manga...so you never know.
When someone's a loser, they show it through their actions.