MY daughter is 2 next month. She sleeps through the night and in a cot. She does have a dummy for sleep time only. She has been an early riser for a while and at the moment, it's 5 am (sometimes 4.45am). My step kids are also waking then and it's far too early for school age children and it's negatively impacting on them (as well as being a royal PIA for us!)
I think it is more to do with her schedule being out of whack than anything else. For example she goes to bed at 6pm and sleeps until 5am. During the day she will sleep anywhere from 2-3.5 hours which I suspect may be too much.
I am bordering on just accepting this but it is challenging for the other kids. Any advice would be hugely appreciated.