Chava and Tzeitel in Fiddler fit your descriptions almost exactly (as does Golde if its a youth production) Any of the female roles in Grease would fit you Lola in Copacabana (if you are familiar with the show) Millie in Thoroughly Modern Millie
That's all I can think of going through the CDs I have on my computer.
Anyone familiar with "Time Heals Everything" from Mack and Mable? Not really age appropriate from the show (according to my vocal coach) but it's a good range for me.
You might want to consider a song from the show "Violet." The title suits your description. It should fit comfortably with you. Another pointer, be careful not to do something too up to date. Trust me, nobody wants to hear "Still Hurting" from Last Five Years or "I'm Not Afraid of Anything" from Songs for a New World again. Chances are, they've heard it 18 times prior to your audition. Do something original that nobody else is planning on doing. Chances are it will stay fresh in their minds if they really liked the song. But look at "Violet."