Why do people lie and want attention so badly?

Me and my cousin are in the 11th grade in high school. She pretty and all the guys like her but I'm the awkward one who's 5"9 and very skinny && sometimes boys would make fun of me && tell me I need surgery and other stuff. It hurts when people say stuff like that but I don't really care cause I could be a model while most of them are on drugs. Anyways she would lie to our friends cause we have some of the same friends and tell them that her mom is a doctor and would makeup stories saying she have the newest iPhone. Her mom isn't a doctor she works for home health aid and doesn't really make that much money to support 5 kids. But the funny thing Is that she always have the newest and most expensive shoes and clothes. && most of the time her mother is home. I don't understand where she get money to buy stuff like that from and she's very educated girl who pass all of her classes. But I don't see the need to lie when you have everything already like boys like her and would talk to her. I'm pretty too && I have friends but I get treated like *** to some people && I don't lie.
I think she's jealous of me because I have people that says mean things to me but then some tells me that I could be a model && everything I do she would do like if I buy a shirt she would go and buy the exact one. And she would do anything for attention.

Compulsive liar, maybe?