It sounds like you are getting to the right kinds of doctors -- but maybe not the right individual doctors. I would get a different orthopedic doctor's opinion. Ask for an ortho. doctor who specializes in sports injuries. Be sure that first you get copies of all the x-rays, scans and MRIs that have already been done! That way, your daughter might not have to undergo all those tests again. Have copies of them ready to show a new orthopedist, who might interpret them differently. Ask if this could be an infection rather than bone or muscle -- there could be an infection that she doesn't feel until she moves the muscles or bones involved in the infection.
By the way, did the ob/gyn do any forms of scans, or just a general checkup and manual exam? Just something to consider. But since this only flares up when she moves certain ways for sports, it sounds more muscular/bone related than gyn. related.
I would not let it go but would be assertive about getting all the records and scans so far, and finding a new doctor. I also would ask to see someone who specializes in sports injuries, not a general orthopedist.