D.K.
I loved trail mix when I was a new mommy. Especially the ones that have raisins and a few m&m's in it. Those made it something I liked to eat without adding too terribly much in the way of calories. Trail mix is fantastically healthy and super easy to just have sitting around so you can grab a handful here and there. I also stocked up on Luna Bars (but if she's having a boy she should go easy on these, as I discovered that too much soy passed through breastmilk is actually unhealthy for boys' reproductive systems) Nature Valley granola bars, string cheese, fresh fruit (I always craved oranges through my pregnancies and the early days of nursing), prepared fresh veggies (like carrot sticks already peeled and cut), yogurt, Power Bars (although these are a bit of a carb and calorie load each one can hold you for quite some time), also don't forget things like Crystal Light To Go packs since they make drinking tons of water a bit less of a chore.
Also, if you want a few great freezer items, make a few casseroles and store in some Glad plastic ware with reheating instructions written on the container in sharpie, you can do this with chili too and lots of other simple dishes. I'm sure she'd really appreciate having a few meals on stand-by so she will have contingency plans for dinner if her day with baby gets too hectic.