What makes shy people snap?

like do they snap if they had enough or something?
i know this is quite an ignorant question but im just curious because there's a person in my class that gets constantly teased and looks quite annoyed but doesn't do anything but ignore them but she looks really hurt by them though and a few days a go she looks like she was going to snap and have a go at them. I want to help her , I even ask my friends but they are just like forget her I don`t care but I that is really horrible but if I do help her most people around me would be like what the hell are you doing.

Thank you for reading if you did :)

She may snap as you suggest but even if she doesn't there's no reason why she should endure such abuse. You are to be commended for thinking about how this makes her feel. Some times thinking people have to make a choice between what is right and what is popular. The strength of any society can be measured by how it treats the weakest among them. Explain that concept to your friends and try to enlist their help on her behalf.