A.B.
Get a book called Healthy Sleep Habits, Happy Child. Try to get her parents on board for the methods, although as long as you are consistent and have her on a regular basis you should be able to effect a change just when you have her. From what I remember last time I read it (and that's been once with each child) a four month old shouldn't be awake more than two hours at a time, and total shouldn't be awake more than about 8 hours a day. The rest of the time she should be asleep. It varies per child, of course, but that's the general guideline.