Help! Im entering a contest and dont have a song to sing, what should I sing?

Im 12, entering a contest for my voice, and I have a high voice. I can sing some alto, but I like soprano. Either pop or country, a girl song please. I was thinking, Hilary Duff, Christina Aguleira, and Shania Twain, and Carrie UNderwood, but I need more. HELP! I need it fast to!