She's not uppity or snobbish. That was just a front of their first meeting because she also didn't like the idea of being forced to marry someone. She made that cover to get the MC to break it off. She's a tsundere, if anything. She's capable, but also proud and as the old saying goes "Pride comes before the fall." Since then, however, she's been more accepting of him and sees his charm. But because they want to live life on their terms, they are still conspiring against their grandparents's conspiracy.