Elaine, we sailed on the Wonder in Feb. (I have a review on this site, and on my own site at www.knowlton.org/travel)
. From our experience (and that of our friends who traveled with us), I would say not to worry. Check with your doctorto make sure it's ok for your daughter, but I would suggest having a supply of Bonine with you just in case. Often that route is quite smooth and there should be no problem at all.
The best thing to do is NOT to suggest to her that she will have a problem. Our friend's daughter was convinced she would get sick, so she felt that way the first night, although there was almost no motion to detect! The next day, when she had other things to do, she was fine (and she dealt with the little boat going to the snorkel excursion without any meds at all.) She made no mention of motion sickness the entire rest of the cruise.