I think my favorite Rose Ball outfit of hers was last year's. She looked absolutely stunning. But she's either hit or miss anyway. Too often, her look is just matronly and not age-appropriate. And if not that, it's boring. Always black and always Chanel. There are so many other awesome (and, ahem, better IMO) designers than Karl---McQueen, Saab, Yves Saint Laurent, Oscar de la Renta, Andrew Gn. But I'm ranting now. Sorry.
The best thing is you can never go wrong with a neat, chic equestrian outfit. That is why I love this thread.