I doubt anyone here can tell you if your dd will like something or not. Have you researched exactly what CP is?? It is a telling of the life of Christ...basically. A large, multi-school choir processes in, with candles. There are trumpeters along the sides of th theater. There is a full orchestra, with a smaller choir of WDW CMs. A guest narrator then reads various approprite passages from the New Testament....the choirs then sing an appropriate piece of music that augments the reading.
If your dd enjoys holiday/church music, then she will most likely enjoy the performance. It is about 45 mins long...and you do have to wait in line to be seated. And if you haven't purchased a CP pkg, then you'll be waiting in the standby line, which can be lengthy, depending on time of show and the particular narrator.
You can also just stand along the sidewalk, behind the theater, and watch/listen from there. It's not quite the same, but it is an option. I know that last year, when Whoopi was narrating, the people standing outside the theater made it almost impossible to get past the area!!!!