Ditto Veronica P. below.
Remember, hormonal changes, occurs all the time.
Not only in Tweens or Teens.
9-12 years old, are the Tween ages.
And some 9 year olds get their periods at this age.
This is per my daughter's Teachers.
My daughter is 10.
She gets moody too.
BUT I KNOW when it is due to hormones or her just being tired or hungry.
And I also, inform my Husband. Because as you know, "men" do not know these things. They don't even understand a PMS'ing woman.
So, for me, I want to make sure, my Husband KNOWS about the changes in a girl, especially at this age, and per "moods." It is not just her being a fussy monster.
Get the "American Girl" book series. It is for this age, and the Mom. It is age appropriate and explains all the changes in girls this age.
I got it for my daughter since she was about 7.
She likes, these books.
And we talk about it.
Actually growing boobs, and having underarm smells, and having pubic hair, is not the only changes the occurs. It is also the entire, bodily system. Changing. AND the emotional development as well and cognition etc.
The National Geographic Magazine, had a great article on the Teenage brain/changes. Here is the link for the article: