I tend to agree with Crystalboo that they still need at least a rest (if not a sleep) until school aged. I also agree that this is probably a phase, given that it sounds as though she is usually a pretty good day sleeper. My method is to put them in their rooms for a rest/sleep every day at around the same time. If they don't want a sleep, fine, but they need to stay in their room for at least an hour for some down time (with books, cars, dolls, puzzles ect). At most creches/daycare ALL children must rest everyday after lunch under the age of 5. Both mum and child need it, whether they know it or not! So keep doing it even if she doesn't want to sleep everyday.