This is going to sound cliched, but you say she's a terrible homemaker. How are the household chores divided in your house? From your description of her day it sounds to me like she works outside the home, is that right?
I'll be honest with you, women more easily than men can simply be too tired to have sex. It becomes the final chore of the day when a woman is too frazzled. If you can help more (i.e. you're not already doing your fair share of the work) it might really help, especially when there's a baby in the house.
