I have to be honest, having 3 kids, I never felt less like wearing lingerie than when I was pregnant. I felt beautiful and attractive, it's just that lingerie isn't made for the way a pregnant woman's body changes, and little of it is breastfeeding friendly. My main concern for many years, while pregnant and nursing my kids was "can I nurse in this?" or "will this look nice over my preggie belly, my huger boobs and my rapidly expanding butt?"
Plus sizes did NOT fit me while I was pregnant, they were too big nor did my regular sized lingerie. I just stuck with comfortable cotton night gowns (as you usually sweat like a pig when you are pregnant and for at least a few weeks after the baby is born.
Does she have a wedding registry? We're going to my nephew and his pregnant bride to be's wedding soon, and I'm just going to grab something off the registry or probably stick to what most new couples, especially those with a new baby need... CASH!