If she is still nursing up to 8 times a day, then I would recommend staying in the 1700-1800 range. La Leche League recommends nursing mothers not dip below that amount, or it can affect your milk production. Because of the calories burned through nursing, it would be equivalent to you eating about 1500 a day (what you wanted) if you were NOT nursing. Does that make sense?
I would also recommend that you try to eat as healthy as you can, and to start SOME form of exercising. it makes a world of difference in your body, and in the way that you feel. If time is a factor, there are many dvds out there called "Quick Fix" or "10 Minute Solution" and the like, that have short 10 minute workouts on them. It may not seem like a lot, but if you did one three times a week, that is a half hour over the course of the week that you were not doing before.