No, I don't think the photo is inappropriate at all. If you had composed or cropped the photo so that her crotch area was the main focus of the photo, then it would be inappropriate. The photo you posted just shows a cheerleader/dancer doing a typical pose for her activity. The "spankys" under the skirt are part of the uniform and they are worn to cover parts of the body that will be willingly and openly exposed because of the various moves the wearer will make during her routine. She is also wearing tights that are like pantyhose which completely cover her private areas under the spankys as well as her legs, (much like ice skaters wear). This girl is covering more of her body than a gymnast or swimmer.
Catching a glimpse, (or a photo for that matter), of a performer/athlete like this is not like looking up a girl's skirt at the mall. Anyone wearing a dress or skirt has the reasonable right to privacy concerning her body under the garment. The girl at the mall does not intend to have that part of her body visible to the people around her, therefore an upskirt photo in that case is not only inappropriate but unlawful. The girl in your photo as well as her parents, her coach and her school all fully know that her crotch and butt are going to show during her performance and all of them apparently consent to that and are satisfied that she is reasonably covered.
Still, I do agree that some photos may be questionable as to good taste and common decency. If a photo is unflattering or tends to accentuate a feature in a way that the subject would most likely find uncomfortable, I think it is not only appropriate but necessary to either not publish/share the photo or to correct the blemish. For example, on two different occasions I have taken the liberty to use the healing brush in pp to save a good photo, both were girl volleyball players. Once, to hide the "foot of a humped, desert dwelling mammal" and the other to smooth out a white jersey that was a bit too bumpy. No one ever noticed the fix and I saved the shots.
Just my two cents. I don't care to argue my points but I thought I would still share them.