It shouldn't matter that her stomach isn't flat. Mine isn't either anymore! I'd worry less about
finding a garment to cover up any leaks, and more about
why she's leaking in the first place. It could be as simple as adding a convex insert or using paste or Eakin seals to prevent any leakage. I had a lot of leaks in the beginning as well, but haven't had a leak in public in almost 20 years! Adding a convex insert and using paste did the trick for me. But, there are a lot of other options, and I'm sure others here will follow with their recommendations.
Remember, EVERY problem has a solution!