Why do people do this to me?

So theres a girl at my school named mandy thats so pretty. Girls always just randomely say to me you and her should be best friends, you remind me of mandy, your style reminds me of mandy but your prettier than her, when i walked into a clroom some guy was like hey theres mandy and some other guy was like no thats not her. I think everything about hers better than me tho shes taller than me, shes outgoing and i am really shy, all the guys talk to her, shes a good dancer, and shes prettier than me why do i always get compared to her it bothers me. All the guys think i am a because i told my friend a secret and i thought i trusted her but she went out and told the whole school . I hate being compared to her shes confident i am not i can never be as good as her they dont think shes a either