a plastic
A plastic is a fake person, like a lying, money-hungry, shallow fake person. They act like they're super cool, but deep down, they're just sad, fake, and totally clueless.
My cousin is a total plastic. She spends $50 on a lip gloss and then cries in the bathroom.
My best friend is a plastic. She lies to everyone and still expects people to like her.
My neighbor is a plastic. She puts on 10 layers of makeup and still looks like a raccoon.