Mine isn't this old yet so this may sound like naive advice, but i'll give it a go!
Try doing somthing fun to keep her awake a bit longer, go to friends houses, to a restaurant with a play centre, or a soft play centre, most are open till six. you could do some of these after nusery even. Try o put her bedtime back gradually by half an hour ech time.
When she wakes in the morning, don't bring her into your bed, she's formed a habit and it is possible to break it. When she call you, go in, say its still night time (good that its still dark!), mummy is going back to bed now. She doesn't know the difference in times between you outting her back to bed if its the middle of the night or if its 5am, thats you making those decisions, so pretend its still 1am or something. if she still calls for you i would go and say its still night time, mummy is trying to sleep and give her something to do, like a book or something with a soft light on, she may amuse herself for a while, or better still fall asleep cos she's bored.
Personally i would treat it like PU/PD for younger tots, warn hubby he may be in for a few bad nights to begin with, but it should soon work itself out so will be worth all the hard work.
Good luck!!!