What it took me days to figure out, is that she is saying "Empty bellies, 'stead of full," which I found out when we were watching Annie for the thousandth time. It's one of the lines from "It's a Hard Knock Life." I don't know why that's her favorite line, but she sings it constantly.
I also don't know why it never fails to make me smile. Maybe it's her voice. Maybe it's because she's just starting to communicate better and do things like copy movies and songs.
Or maybe it's just because I find her so stinking cute.