The size small would definitely be too big for your girl now. Ruby is 3 1/2 lbs and it is too big for her. We've got the purple opera dress in the same size small and it fits, but then it's got the rouching (gathered) bodice. Most likely your girl would wear an X-small in most of their designs when she is full grown (going by her current weight/age). For now she would probably wear an xx-small.
I order mine from their website. And, I believe they are currently running a sale.
http://www.iseespot.com/bNetStore/Te...5=2&Param11=13