I' m not a girl,not yet a woman是什么意思

应是：我不是女孩子了，我已经长大了，但我还不算是成熟的女人。
你可以根据布兰妮的歌词综合理解一下：
I used to think
I had the answers to everything
Mm but now I know
That life doesn't always go my way
Yeah
Feels like I'm caught in the middle
That's when I realize
I'm not a girl
Not yet a woman
All I need is time
A moment that is mine
While I'm in between
I'm not a girl
There is no need to protect me
It's time that I
Learned to face up to this on my own woah
I've seen so much more than you know now
So don't tell me to shut my eyes
I'm not a girl
(not a girl,not yet a woman )
Not yet a woman
(Just trying to find the woman in me)
All I need is time
A moment that is mine
While I'm in between
I'm not a girl
But if you look at me closely
You will see that in my eyes
This girl will always find her way
I'm n