I disagree with the premise.
Tznius does not mean that a woman is supposed to conduct herself in a way that is unattractive. It does not mean that a woman is not supposed to try to make herself look nice.
I generally like the quote above from Rabbi Blumenkranz, which I take to mean that a woman should look attractive, just not in a way that attracts extra attention. (like flashy clothes, etc.)
Wearing makeup is part of being a woman, and feeling like a woman. I am surprised when people object to young girls wearing makeup. Do they object to young girls brushing their hair?