I've been hearing from a bunch of people that this little apron dress always turns out too large for the bunny (or siamese kitty, since the pattern is nearly the same). I'm not sure why, because I never have any trouble with the pattern, and I don't think I knit all that tightly. However, if you knit a bit looser than average, try going down a needle size or two (to 2.25 - 2.5mm), and adding 3-5 rows to the skirt.
By the way, here's the instructions for the little pocket:
Cast on 10 sts. Starting with a purl row, work 6 rows in st st. Next row: k across. Next row: k5, yo, k5. Next row: k across. Cast off all sts. Sew pocket to dress front, and add button.