No, you are exactly right. I told them they can work something out based on my previous experience, but apparently I was wrong.
I'm definitely sympathetic to the awkwardness of the situation. You didn't lie, but it is true that maybe they changed their policy BECAUSE of the girls you previously mentioned. My guess is it didn't work out or something or they realized it is taking spots from those who would fully participate. But I also suspect that if they continue to argue and act like it's unreasonable, they are going to paint themselves as people who should not be invited to team ever. If she's never done preteam and isn't ready to commit, it would be better to approach the office staff from the perspective of "what would be a class where she could work TOWARDS team but wouldn't require competing?" Surely they have some class where the kids in the bronze team come from.