We ha e always been 'matter of fact' towards my daughters when they were younger, and now grown with families of their own, Grandchildren too. I would often find one of my girls looking through one of my medical textbooks that I often used at work for educating clients in a Mental.health setting. If ever they needed to ask a question regarding their.own bodies, that was fine, and a simple honest answer soon put their mind at ease.
Like the designated toilets that schools now have, we have always had a shelf in the under sink Cloakroom cupboard that is well stocked and replenished as needed with Girls Supplies!
There is also things like hand cream, wet wipes, and even spare new lip balms in there, and they know that they dont need to ask if ever they need to use any of them. Being as about 8 different females know about Grandma's cupboard, including my adult daughters, I have no idea who is using the supplies, and just top up as needed. They do know though that its ok to talk to.me if ever they need to sort out a concern or a problem.