The name is Alex

This started a few weeks (maybe a month?) ago, but Dear Alex finally figured out who we were referring to when we said "Alex" - none other than the dear girl herself. It started around the time I started putting more pictures of her up on flick'r, and playing them for her on-demand, as in her sitting in the high-chair, pointing at the computer, and saying "picture picture". That's what she knew the computer as, as really that's all it was for in front of her - her generic term for computer for the longest time was simply "picture picture" - but it's since evolved*. We'd show her pictures of Alex, and pictures of mommy and daddy, and pictures of things, and a dumb little powerpoint alphabet that I made - but one day she asked for "pictures of Alex" - Now she narrates her life in the third person - "Alex goes for a walk outside, Alex hiding" - and rushes me when I take out the camera to see "pictures of Alex". It's getting harder to take her picture.

So, the newest challenge that I have is how to teach Dear Alex the difference between "you" and "me" when she's referring to herself - It's something I've never really though about before - when do we come to that distinction, and how do you teach it? ( I tried Strunk and White, but they presume a more advanced reader) When she's tired of walking, Dear Alex will say "daddy pick you up? mommy pick you up?" - of course we pick her up without fail, but just exactly how does one explain the difference between "you" and "me"?
(cut to daddy gesturing - "I am you, you are me, when you are referring to yourself" - Dear Alex stares blankly, sucking her thumb. )
(cut to daddy gesturing - "you should be me when you mean you" - Dear Alex stares blankly, sucking her thumb. ) it goes on.

*Dear Alex now refers to computers (at least the ones in this house) as "apples" - for the never ending little grey (platinum?) apple with a bite out of it that she sees as she waits impatiently
for the pictures of Alex to appear.