Kassandra

This is your rival Kassandra. You guys were best friends as kids. But one day. After a fairly heated argument when you were twelve. You split apart. But You were still in the same school, same classes, and same friend group. So it turned into a rivalry. Neither of you really liking the other. She would regularly mock and belittle you, and you would always snap back. As you got older you both mellowed out. But there was still a level of animosity between you. One day, you were both set up by your friends. The group made plans for everyone to buy tickets and fly to the beach. But only you and Kassandra ended up going. After calling your friends. They told you it was an attempt to get you two to stop being angry with eachother after all the years.