Predictably I shall wade in with the maiden aunt view.
When I was young, many moons ago, foundation was something which old ladies wore and all the magazines advised women under 30 to avoid as it would not only clog pores but it wasn't a good look either. I am actually shocked when I see young (by which I mean under 15 ) girls caked in the stuff...I wonder why their mothers haven't either told them how awful it looks, or at least shown them how to apply it a bit more sparingly. It is one thing to cover up blemishes, quite another to look like an orange flavour iced bun. And no, definitely not at school. Bleah.
Ditto mascara...why blonde girls are wearing black mascara is another mystery because it tends to look ghastly. I think if you are going to let pre pubescent girls wear make up then you should show them how to apply it in moderation and which colours to choose. It is so sad that pretty little things of 13 and 14 are making themselves look so much worse by doing this...when you get to my age you would give anything for the kind of skin that doesn't need coating in artifice. It sounds like your in-car conversations were very sensible Marylou. If more mothers took responsibility like this perhaps there wouldn't be so much pressure on girls to waste time and money on things which detract from their natural beauty.
That said, I guess there is no point being unrealistic and everything in moderation...but personally I would have been unhappy if DD had wanted to wear it much before 14 or 15, and I do think mothers have a responsibility to ensure their daughters are aware of what kind of image their clothes and make up are giving out. One or two of my little Year 7s have had some unwelcome attention from older males when they have gone out in particular items of skimpy wear.
At the school I teach in, girls rarely wear make up...it has a poor socio economic profile and I don't think they can afford it. That said, one of my Year 9s proudly showed me her belly piercing, and several boys I teach have those big earrings that make massive holes in their ears, like the Masai wear. At my DD's indie make up is allowed for covering up blemishes only, and girls are issued with tissues and soap if they come caked in it. Being an old fashioned mother, I am happy with that. I bought DD some decent make up (she was 15) and showed her how to put it on, but she very rarely bothers.