Thank you all for your advice. Of course I'm going to get the proper paperwork because I don't want to end up on shore or in a mexican jail of some sort

I guess my thought that her dad had signed off on getting her a passport would have been enough but I do understand with the kidnapping situations one never know. Out of curiosity in this day and age when you don't know who the father is or he is deceased I wonder what happens.
I will say that I had contacted Carnival and they told me I wouldn't have to worry about it but sent me a form giving her permission to travel in a youth group. That's not a secure enough feeling for me as my gut says I better have the correct paperwork just in case.
Thanks again for your help.