This is a creative take on the prompt, @wongi. You establish the personality types quickly in the story so that we are prepared for the calamity that befalls Julia. Not only does her arrogance--refusing to wear a mask--get her into trouble, but her bullying contributes to the accident. If she hadn't startled her classmate, the corrosive chemical never would have splashed into her mouth.
You set up a conflict, tension between Julia and Vivian, early. You resolve that conflict well.
Good job.
Thank you so much