Hi M.,
I can truly relate, as I have been going through this for nearly a year. Although I have not yet not solved the problem, I can share my advice, given what has NOT worked well for me!
First and foremost, I would agree with the folks who say you need to let her cry it out. Set a time when you will go (6 is reasonable) and don't show up before then. Secondly, you may want to experiment with pushing her bedtime earlier...if she is waking up early due to being overtired, it may help. This has worked at times for my son. Finally, I would also strongly recommend the Marc Weissbluth book mentioned - "Healthy Sleep, Happy Baby" - which provides further guidance along these lines. I doubt my son would sleep at all if not for this.
If you need further encouragement on why you SHOULD let him cry it out, read on...
My son was always an early riser - on average by 6 am or so. However last winter when he turned 2, I went through something similar to you. He got sick and started getting up at 4-4:30 for a few nights. I did not implement a "cry it out plan" immediately as I thought it would get better. As a result, I have been getting up at or before 5:30 for most of the year! I thought it would improve on its own, but it did not, and now he is getting up at 4:30 because of the time change. I now realize that "cry it out" is the only thing that will work, but unfortunately it will be 10 times harder now than it would have been months ago.
So, I would urge you to act swiftly, endure a few mornings of pain and avoid losing a year of sleep!
Good luck.