The article says that basically the news reporters wanted something to talk about so the "made-up" a story about people bashing her shorts. No one anywhere can find a story that actually does it.
You have to keep in mind that this is sort of a fashion statement for a first lady. It's not very often (if ever) that a first lady was photographed in shorts.
With all that being said...WHO CARES!?!?!?!?