There are two bakeries in Richardson that make good cakes. One is The Cake Lady (think this is correct), the other the Chocolate Angel. Both are located in the same strip center at Nantucket and W. Campbell, southeast side of Nantucket. You have to drive around the buildings to find. Both are extremely busy, so you will need to order much more in advance than places like Sam's, Costco, and other grocers. One grocer that has made good cakes in Plano is Fiesta at Parker and Ave. K. Costco also makes good cakes if you have many to serve. I have ordered cakes from Willie Mays at Park and Custard. Some have turned out good, others not so good. Friends have mentioned Celebrity Bakery at Parker and Preston, but they have been pricey.
I hope this helps. I wish you the best for your little girl's birthday. Such a precious and worthy even!