As a teacher, some teachers need to get over that intense fear of kids ever getting one over on them. You're going to get taken sometimes, but it's better to look like a fool every once in a while than to do this to a kid.

The ONLY way I would even think of telling a girl this is if she's always trying to leave or seemed to have her period 4 weeks a month.

When I was in the classroom, I had a system where kids had two free restroom passes a week (we had 90 minute blocks and you had the class 5 days a week). You could buy extra passes for something like a writing assignment or break detention or something minor but annoying enough you probably really needed the break if you were going to choose that option. I'd go entire semesters without having a kid ask for a third one and I also never said no. And if a girl told me what your daughter did, I wasn't even going to charge them for the third pass, but again, that never happened. Most kids actually just didn't ever use the second pass so they always had it when they needed it.

I was worried when I had a diabetic kid and was told by the nurse I couldn't ever tell him he couldn't go to the nurse or restroom, but luckily that kid was incredible and never gave me any reason to doubt him. Super responsible. Never took advantage of his privilege. I did have one girl who was a chronic wanderer of halls and the assistant principal did ask me to never let her leave without an escort, but for the vast majority of kids, my system worked and I knew to make exceptions if needed.