Why do girls hate me so much?

[Blundt Cake]

They're insecure and jealous.

Be aware--- this behavior doesn't change as you get older.
Adult "grown" woman are just as vicious and evil, if not more so.
When you're older, the stakes are higher: they will bully you out of a job or promotion, spread rumors to ruin your reputation, gossip to denigrate your relationship or marriage, make it miserable for you to be in a club or group.
And as these types of women start showing the signs of aging, they actually get worse, because then they pick on younger, prettier women.

My advice is you just gotta life your life, and don't let ANYONE stop you from being the best you can be. People try to bring you down because they believe you're above them. Stay above them, and carry on. But be aware-- you're 18 now. It won't be much different when you're 48, especially if you're smart, pretty, feminine, sweet, etc.