I do a lot of theatre in my area and some of it involves kids. Most of them have a difficult time preparing a song for the audition. So, I would have her sing Happy Birthday. It's short, everybody knows it (I think) and it will let them know if she can sing in tune....Kids sing it at auditions all the time, in fact, if I have a kid auditioning with a song that sounds horrible, I will often say, "That was great, now how about singing Happy Birthday for me." More often than not, they will sound a lot better.

Frank