Babies can be helped to sleep better by making sure they get enough rest during the day.
Most babies don't require more than 12 hours of rest, but some do need as many as 14-15 hours in order to feel their best.
Too little sleep is just like a toddler not eating or drinking water: it leads to crankiness and poor health in both cases.
Crackdown on naps that last less than 30 minutes and try coaxing your child into taking one more nap later in the day if she's still struggling at bedtime (the goal should eventually be for her to fall asleep without being rocked, nursed, or nursed back).