@(you need an account to see links)
From what I've seen, you're a genuinely talented, kind-hearted, and sweet individual. You're really pretty, and obviously really smart to have won those medals. It really probably was just that - jealousy. No matter how nice you are to others, how much you try to do right by everyone, there will always be someone out there who's envious of your successes and will try to undermine you when given the chance. My father used to tell me a story about how he was best friends with a classmate who ended up being one of his worst enemies - he'd take things my father confided in him and use them against him, and even voted against my dad in secret when it was time to choose a captain for one of the school's sports teams. I don't quite get why anyone would want to condemn another person for their successes, but some people are just like that, I guess. It makes them feel better about not being as good as you. It's outrageous that they even tried using your ex against you to make you feel bad, but some people probably just take longer than others to mature. ~_~
Even if it's hard to avoid those girls, don't let them get to your head. All you need to know is that they're the ones being petty, and you're the one being true to yourself. Have you considered applying to an out of state university? It might give you the chance to connect with other people outside your current circle if you're looking for new friends.
We're always here for you if you want to chat! I find the friendships I make online tend to be a lot more meaningful than many of my real life ones sometimes.