What is this behavior?

I was wondering just what exactly my cockatiel is doing. When she's on my shoulder and I talk to her she puts her head down and makes a low tone noise, almost like a growling...yet she seems very happy, no the least bit angry. Also yesterday I got her out and she climbed up to my shoulder and I turned my head to her and she put her head down and her wings out, kinda like she was hugging me, but I really don't think that's what she did LOL. Just curious to see what some of these behaviors mean as I haven't had a cockatiel since I was little. She is 3 months old, and I'm not even sure it's a she. That's just what I've been told, so I have no idea...for now I'm calling it a "her".

It's happened to me before when I had a rabbit, they told me it was a girl, so I named her molly...later on down the road I noticed an "extra attachment" and so we named him Mo..short for molly since he knew his name.
I'm also looking for a name for my cockatiel, I've had her since Sunday and she's still nameless...so I'm open to any ideas anyone might have, I'd really appreciate it.
And what are the chances of her talking? I had her whistling the first day I had her. And how long should I work on one tune, before I try to teach her a new one? Thanks for taking time out to read this post.
-Mandi