Okay, this is my first post since I just found this wonderful site and joined!
I have six children, and have tandem nursed almost all of them. My four y/o still occasionally nurses for comfort, even now, and was still breastfeeding several times a day when I was pregnant with my youngest (now 17 mos). You have to be super careful about nutrition and water intake, because you're growing a new baby while nourishing another one.
Also, at some point, your milk begins to come in a bit stronger again, due to all the hormones. It also alters the flavor of the milk some--some children don't mind this, some wean themselves once there's more milk than they're used to AND it tastes differently (I've had both experiences).
Breastfeeding while you're pregnant is a wonderful experience, but like all of the moments in motherhood, has it's ups and downs. Breasts can get sore and swollen and you can get tired out. Also, it's a little daunting trying to find a way for a toddler to nurse around a big, pregnant belly! lol Luckily, most toddlers like acrobatic nursing, so they sometimes even think it's a game!
Hope this helps. Enjoy breastfeeding your daughter--now and in the future. :)