I highly recommend some sort of pretty robe. You can grab it when you head into the baby's room for a night feeding (like I'm still doing at 11 months, I'll just add). You can cover those old sweats with it (but you really should just toss those, come to think of it). And when the baby actually goes down for a nap, one of these robes will help your relationship with your husband. Get one in a pattern so the stains don't show. Come on moms, wouldn't one of these make you feel instantly more glamorous? (Both are from Anthropologie.)
A new mom is also going to need a lovely little housedress. "Housedress" does not have to be a scary word. It's something pretty and forgiving and simple to slip into. These are both from the sleepwear section of the Anthropologie site.
Or a nursing pajama set, like this .
And if you're a super, super, duper good friend, get her a beautiful nursing dress to go out on the town in.... like this by Isabella Oliver. It is the only piece of clothing designed for nursing that is truly beautiful (that I've ever seen, anyway).