I would go with the bigger size. (I believe that would be 1-2). Like someone else said on here, the 1-2 is a blend between 1 and 2, and not some 1s and some 2s. It is better to go a little larger than the exact fit, when you're ordering a case from Diapers.com. We do that as well. Also, if she is breastfeeding, the bigger diaper is better for blowouts (because the stool gets pretty loose sometimes). LOL! I am pretty loyal to the Pampers brand, because of the Swaddlers they have, and also because of the reward points. We plan on redeeming them for Leggos, L.L. Bean, or a restaurant gift card. LOL! If you need to order something extra, in order to qualify for the free shipping, you can always order clothes. That's what I did with my little guy. I got 3 t-shirts in his last order, and they were comparably priced with places like Target or WalMart. I wouldn't buy more than one case of diapers at a time, though.