loooong. Just a warning
Fwiw: Just because something is "commonly" done doesn't make it right or appropriate.
Let's take some practical points first:
Letting a little girl wear high heeled sandals just increases the likelihood that she will (1) break her ankle even younger than if she started wearing them in high school or older and (2) she will start shortening her achillies tendon even younger. Ever see old women who HAVE to wear high heeled slippers because their legs hurt if they wear flats? Well, it's because their tendons were shortened by not having to stretch them out by wearing flats for most of their lives.
Giving her makeup to wear exposes her to a whole boatload of lovely pigments and 'vehicles' for the pigments that usually are made out of
metals and petroleum products. This is very true of all those lip products. Lip gloss is mostly petroleum jelly. Calling it vaseline does NOT change the fact that when you eat, you're getting a petroleum product into your mouth. This stuff gets into the mouth and eyes, gets inhaled and if the lips crack, can get into the bloodstream.
Nail polish has lots of toxic fume-laden substances AND the above mentioned pigments. Ummm.
Formaldehyde. Xylene. Loooovely. And SO pretty.

:
And, even if none of these things causes cancer or whathaveyou, she could get an allergic reaction. If you cd'ed because you don't want to let your dd be in contact with gels and perfumes, why would you let her/encourage her to wear makeup?
Now, an, apparently, old-fashioned perspective. NOT a hijack, please read to the end.

(Might as well tell you, I am 37.) My mother was a clothes horse and ALWAYS wore makeup. HOWEVER, rules about what I could and couldn't wear were pretty set. The main thing was that all clothing is drag (my phrase, NOT my mother's

). That is, clothing is a costume. Whether you like it or not, clothing sends a message. This is true for men and women. So, I regard clothing as a "uniform" or "drag", dressing for a role.
Regardless of what the "fashion dictates" or "well, it is in all the stores" or whatever, you STILL have to evaluate the message clothes are sending. (And, before I get any further, I've got to say, No, I don't think any clothing "invites" attacks...nor will preventing a daughter from dressing like Lolita keep her from being molested...that is not a "role" that is a tragedy. I'm just sticking this in because I've had conversations about this topic with people who claim that I'm saying that if you dress sexy you're 'asking for it' -- which I'm not.)
I do not dress to 'express myself'; I let my mouth do that for me.
Messages I usually think about are: the Eve Arden (she was in Our Miss Brooks and a whole bunch of movies) suits I wear to the office. No jewelry. A practical Timex watch with a black leather band. A solid color hairband or my hair in a bun. No makeup. Practical. Elegant with no attention drawn to something obviously expensive. Not a "mini-man" suit. Definately female. Whether or not I approve of it, the guys I work with are NOT going to totally ignore the fact I'm female. So, I dress a bit for power plays. This can be a way to set other people a bit on edge. I sometimes find this handy in negotiating sessions and other meetings. I work in a fairly adversarial business.
When I go out on a job site, I dress for THAT occasion (I keep a change of clothes at the office): generously man-tailored khaki trousers with pockets for various equipment I need to stick in them, men's style tailored shirts, steel toed boots, hard hat, same watch. No jewlery. No makeup. Nothing that'll get caught in machinery.
At home, hosting my annual winter party: Dressed to the nines as much like Mae West as possible, and I get my hair done the afternoon of. Three inch lavender suede heels or whatever I think goes with whatever clevage-enhancing dress I've got on. Old fashioned garter belt in red lace and fancy silk (not nylon) stockings. Some Beauty Without Cruelty or Dr. Haushka's makeup.
When I was a child (and, yes, I think nine or ten or eleven is a child), I wore simple, conservative dresses and trousers. No bikinis. No heels until I was 12. And then no higher than 1". And no decoration on the shoes, only solid colors. (Went to schools with uniforms, so I didn't need as big a wardrobe as some might have.) Lots of times the dresses I wore were variations on the "middy blouse" or "sailor suit". I think you could safely describe these as modest clothes. Cloting appropriate to the task. Gym clothes for sports. Hiking boots for backpacking, etc. etc.
When I was 12, I was earning quite a bit of money from babysitting and other odd jobs and my mother started letting me wear more daring things as long as I purchased them myself and as long as I wore them only to appropriate places. Not to school. Not out with girlfriends. Even if the friends were wearing the "chippy" stuff (as my mother called it

: ). So, I learned how to put it together to look, when I wanted to and was mentally prepared for it, at least 24 or 25. I kid you not. And I went out with my mother to jazz clubs and all sorts of places that children didn't go. (I had been going along to NOW meetings and lots of other adult places, but these were different. These were "adult" because of the presence of "sins" like alcohol, not "adult" because of possibly being over one's head intellectually.) But, I also learned the power of "a role" and how nice it is to be able to slip out of one role and into another doing something as simple as changing your clothes.
I also had a BAD experience with this. My mother felt my eyebrows needed to be heavily waxed as they made my "face look dirty" in her opinion. The fashion then was thin brows and that's also what suited her. That did not suit my face but that's what I was given and when I stopped plucking them six years later after she had nothing more to say about it, they didn't grow back. So, now I live with her aesthetic on my face.
And I think encouraging little girls to absorb only one role, or to go into a role too early without understanding all the other stuff that goes along with it is really dangerous.
edited for a spelling error.
Follow Mothering