How big were your boys? If they were 8+lbs, your daughter will be in the 7lb range. Personally I would register for no more than 2-3 smalls.
I use to LOVE FB with my DD. I went a little crazy and got 18 small FBs for DS before he was born. When he was born, I used prefolds/covers until the cord fell off. Then I started using FB at night only. Needless to say, I sold them by the time he was 10 weeks old (13-14 pds) at a loss of over 50%. Sad part, they were practically brand new since most had only 3-4 wears. I would have used them more however he's allergic to latex and their elastic has some in it and he would get really bad red marks from them.
Not to mention, what fits on one child perfectly may not on another. For DD, happy heiny fit her lousy. For DS, HH fit the best. DD has no bum or thighs whereas DS has both.
If you want to register for more fun, get a bunch of different diapers so you can see what works for you. Most online stores have a bunch of different brands. I LOVE fattycakes but they are only available from WAHMs. They are slimmer than FB and HHs.
Other brands I can suggest:
HH
VB pockets or AIO. Recommend
flutterbybaby
bumgenious. Some really love these since they are onesize. I hated the fit on DS for the same reason as FB.
Green Acres Designs (again another slim fitting)
Check any other their website and see if there is a local store. Most people won't mind driving to a local place and they are usually more willing to take returns as long as you don't wash them