Is she going to breast feed her baby? They have these new coverups for feeding the baby. I don't know exactly what they are called but some have a bit of boning in them so you can see the baby nursing and straps that attach around your neck so baby can't pull it off and make you flash everyone.
Someone recently told me they love the snap extenters for the onsies, then they can wear them longer.
Of course Diapers, burp cloths, wipes.