Oh I don’t agree with the rule. I think simply stating “No strapless or spaghetti straps” would suffice. But I understand why a high school might need to insist on 2” straps. I also have no sympathy for someone who knew the rules before hand and decided they would not apply to them. If there was a question of the strap width they should have been measured before asking the girl to cover up.
This school has a high percentage of upper-middle class and “1%er” families. It’s really no surprise she thinks she’s above the rules, especially since everyone absolutely has to see her amazing pink dress she bought in Paris.
If she is Mormon, she wouldn’t be able to wear this dress to a church dance, so that’s probably why she was wearing it to a school dance.