No school track uniform today. Just the spandex.
In that case, I agree with you. Not having the loose clothing does give her an aerodynamic advantage and she should be required to wear what the rest of the competitors wear. If that was all she wanted to wear at this meet than I understand the official’s insistence. However, if she was willing to wear the team uniform (or the suggested t-shirt) over the race-skin I wouldn’t see a reason to not let her compete from the viewpoint of competitive fairness.