Why do people who aren’t that great themselves think that they can talk about someone else?

Ok so i have this math class. And this girl is always giving me funny looks and im in college i don’t even know this girl at all, i don’t even know her name. She just sits next to me, that’s the only thing i know about her. Anyways every week my teacher calls people up to class to do a problem on the bored and today was my turn and i know i did the problem right because i checked it with my teacher before i went up to board but i have a hard time explaining how to do math problems because…i dunno there just hard to explain. Anyways when i was done explaining it to the class i went back to my chair and i heard her whisper to her friend, do you think that girl did the problem right because she doesn’t seem like she knows what she doing and then her friend was like no and they just laughed to each other. Even tho they had the same answers as me so obviously i did it right. And later on I heard her talking about how I need to fix my hair even tho i don’t even know what she was talking about because my hair looked fine that day. And she is the one with a fake tan and bleach blonde hair that doesn’t go with her face and skin ton at all and she literally looks like a nerd and im not just saying that because i don’t like her, i just always thought that about her but i didn’t say anything or talk about her cuz i really don’t care how she looks. But she always gives me these dirty looks and talks about me and i don’t even know her. She not that great or pretty herself so what make her think she can do that? I mean im not saying pretty people should do that either but i just don’t get it?

Some people are just like that. They have issues with themselves so they think that by criticizing other people, they’ll feel better about themselves. Don’t let her get to you. You have nothing to worry about because in the long run, not many people are going to like her.