This reminds me of two similar incidents - My mom never advocated for me in school. Like never. Until one day in high school I wore a miniskirt on a game day (on game days the cheerleaders were in really short skirted uniforms). I got in trouble at lunch for the outfit, but just pointed at a cheerleader and said “her skirt is a lot shorter than mine.”. Got sent to the office, my mom picked me up, I figured I was in trouble but no. She told the principal she agreed with me and no she didn’t bring another outfit. We went home.
And at a job, we got a dress code because people were showing up in pyjamas. One of the rules was this weird “4 fingers neckline” no deep necklines? One of our accountants was an older, very old school black man, proper and nerdy and nice. He heard the 4 fingers speech, started grumbling. Later when I passed his desk he had printed out 4 copies of Johnny Cash giving the finger right at the camera, and he just looked at me and said “four fingers!”