The title refers to the fact that, in this era of the strip, she is still maturing. For behold: she has stopped referring to herself in third person! If all the characters did that, then Charlie Brown would be over fifty in the last strip Charles Schulz drew.
The lettering on the crib is interesting. I can't help but think such a thing must seem awfully melancholy when the occupant grows out of it, and it takes up too much room, and it has sold or donated to charity, and so the named crib remains, forever a mute reminder of the childhood of someone obscure we you'll never meet and for all we know died a century ago.
How many stuffed toys does that girl have?!
In the logo in the first panel, there is a weird extra line between the A and the N in PEANUTS. Do you see where the line comes from? Here's a hint: look at the "b" in the word "by" below it.