It might be a good idea to make a muslin of the current bodice, then have your granddaughter try it on. While she’s wearing it, draw directly on the muslin exactly what you want the top of the bodice to look like. Take the muslin apart and cut along your hand drawn line and now you’ve created new patterns. You can actually use the muslin pieces as your pattern piece (just be sure to add seam allowance to the cut line). Then try making another muslin to make sure you’ll be happy with the results. Hope this helps!