Based on the charts, this dress is designed to have a 4″ ease in the chest for size 8. Your daughter’s chest measurement is 1/2″ larger then the size 8. Based on your child’s figure, you might only need to add a wee bit in width and length, or more, depending on her shape. If she’s fairly average or even thin, I would simply add in 1/8″-1/4″to my side seams, about 1/4″ to my shoulder seam and sleeve and possibly another 1/2″ or so at the waist/skirt seam, depending on her height. By adding in the 1/8″-1/4″ to the side seams, you will have added in 1/2″ -1″ in her chest area, putting you at and just above the ease for size 8.
Since you will be doing a muslin, you can check the fit to see if you will need the zipper at the side. If you do need the zipper, you will want to decide the type of zipper finish you want, such as invisible, lapped, centered, etc. that will of course, determine how you finish off that area.
I have not used this pattern, but I have it in my hands. I am hoping to use in the next month or so.
Have fun sewing and I would love to hear how this works for you.
By the way, I don’t know if you have ever seen these instructions, but here is a bit of information on how to size up/down patterns. http://sensibility.com/tips/how-to-resize-a-pattern/
Carol