Why do some people over react when they get a better score once?

Anonymous
So basically at school I was a really smart pupil who always gets better than this girl in Naplan, Selective and all the other tests ( maths, English science etc) . When I get better than her I don't over react or say anything, instead I just mind my business and sometimes comfort her. Though I remember there was one Naplan where she got a tiny bit better than me like one more band 10 (it wasn't band 6) or something and then she just started bragging and kind of just shoved it in my face. Like saying : hahaha you did so bad or I thought you will do better than me or see I am smarter than you now or I am smarter than you think or seems like you have learnt nothing at selective. Basically she was over bragging and I don't really get the reason as it was her first time getting better than me (I don't know if it was luck) , I never put down for her score and she only got like a tiny bit better. I'm here to ask why would she overreact that much despite it being the first time she got better than me in a test and declare that she is improving more than me and that she is smart whilst I am dumb just based on that one test which was probably luck. Is this meant to be normal like I don't get it.

Now I regret not shoving my score of every test into her face.
Why do some people over react when they get a better score once?
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