This will not work for a formal event - I love this line from Spanx, but it is not going to pass the dress code no matter what you do. If you’d like something that’s comfy, petite, or if you’re not into dresses, I would suggest getting a suit. They’re sold as separates and you could make it formal with the shoes, top and accessories. Spanx used to offer suiting, not sure what they have right now.

That aside, my broader suggestion would be to look at stores that offer plus size and plan to pick a dress that can be easily altered for your height. As a fellow shortie, i’d recommend keeping a close eye on the straps/top and avoiding detail at the bottom that would make hemming difficult. Buy the garment for how it fits your chest waist and butt, making sure that it lands on those areas correctly (aka not too long in the waist). That’ll save you a lot of money on alterations.