Sewing for a plus size tween

I have to sew a dress for a tween, going into 7th grade, to wear to a wedding. She chose the Sis Boom Jamie dress pattern it's here in the Oliver & S shop. I met her yesterday and took her measurements chest 38, waist 38 and hips 42. She's about 5'3". It has a fitted waist so I thought it would draw the eye in to look like she has a waist instead of straight up and down. I have only sewn Oliver & S patterns for my granddaughters under age 6. I understand I would start at the waist measurement. I would appreciate any suggestions on how to fit this dress.