oh yes, that's true. maybe you can try the pure pearl powder then, the 100% one.
my son was like that but recently i figured that he kind of overslept and that's why when he has a nightmare he couldn't fall back to sleep because he was actually slept enough. so now i cut down to 1 nap and day and try not to let him sleep for more than 1.5 hr and he's actually a lot better, at least he can slept thru the night from 9:30pm-7pm.
side topic, does your daughter goes to playgroup??