Other than the color, I actually liked the upper part of Elena's outfit at the wedding. It celebrated Spain, her quirkiness in fashion and the styling was beautiful. I think the problem was the lower portion of the dress. If it had been a straighter line/column skirt like the ones worn by the Thai princesses, the bolero would have been the focal point. Even though EVERYONE noticed the bolero, there was no focal point because the big skirt kept drawing attention down. It was just out of proportion, IMO.
And yes, Elena is regrettably unfortunate-looking. But she can look quite pretty in the way Princess Anne, the Princess Royal, can occassionally look quite pleasant and approachable. Besides, Elena has the most fantastic body. A fitted skirt with a bit of a slit to show her amazing legs would have been a much better choice. And yes, a different color.