It is perfectly understandable for you to be concerned about the safety of your daughter. And I hope Meghan's comments will ease your concerns.
However, you must accept that you cannot protect your child from EVERYTHING whether at home, on a cruise, or with family. You and your daughter will be a lot happier the next 14 years if you allow yourself to let go a little. And, she will be going to school soon. It will be a lot easier to let go then if you start now.
I do know exactly how you feel as I have an outgoing daughter as well. Enjoy your cruise and let her enjoy the experience of being around other children other than family.
By the way, are there any other children in your family going on the cruise? Camp Carnival goes up to age 11 so if there are other children in the family in that age range then you won't be leaving her completely alone.