Kids step back and forth with maturity. Just when you are delighting in their self-reliance, honesty and responsibility, they hit a stage where they become secretive, eye-rolling, forgetful and remind you of how juvenile they still are. I'd be careful to celebrate exactly what her accomplishments are without tying it too much to "womanhood." She still has a long way to that point and you can't guaruntee that you'll treat her like an equal grown woman the next few years because you don't know how crazy she might get in those later tween/early teen years.
DD was 9 and finally asked (which was a big deal because she HATES needles.) She was also at an age where I could trust her to take care of them. Just the action of having it done and picking out earrings was special (and a good memory I have of when I had my done at age 12.) We went to lunch just the two of us (no boys) and it was a lovely and memorable girls day.
Maybe you could do something similar with more focus on sharing how proud you are of her current choices and behavior? If you really want it tied to womanhood, you could delay until her first period though that could still be years off. You could make it a page in her scrapbook or tie it with a little girls day with a couple close friends.