I tend to believe it was like a "signature", too. No real thought to her child, but to put her mark on it. More like "I was here". She never considered it could connect back to her because, imo, Casey never thought anyone was smart enough to find Caylee.
It certainly was HER signature. KC loved hearts,and thought "there you go Caylee,I'll bury you with something you love,a little red sticker." Well,it's ALL ABOUT KC,even then. As far as I can tell,it wasn't Caylee who loved hearts,I didn't see hearts all over little Caylees' bedroom. But I did see that KC loved hearts,they were all over her MySpace page. It was to make KC feel better. It had nothing to do with Caylee.
How very,very sad.