After further research this morning, around Munich...

There are lots of large-hipped Bayerisch women, and quite a few wear dirndls. The ways that they seem to make this work is (a) that the pleats on larger-sized dirndl-dresses are deeper, so don't "break" in quite the same way, and (b) women here cleverly break up the vertical transition between waist and hips by accessorizing with something with a strong horizontal line, typically a decorative contrasting apron which hangs down in front and makes a breakline around the back, so the hips don't seem to stick out.