Many, many years ago, somebody invented jeans. The world decided that jeans were a great invention, and the idea caught on like wildfire. Everybody owns at least one comfortable pair of jeans, and the world is a better place for the invention. A while later, someone decided that distressed jeans were the next step forward. That's when people intentionally started wearing faded, frayed jeans, or jeans with holes cut out of the knees and thighs. Now, we've finally arrived at this look. Welcome to the future.
This is the style choice of someone who likes jean shorts, but also likes the comfortable feeling of wearing a full pair of jeans. That's why she's cut away almost the entire middle section, and left just enough material to make sure what's left of the legs doesn't simply fall down around her ankles. The structural integrity probably leaves a lot to be desired, but in a world full of jeans, she can say she owns a pair that's truly one of a kind.