Early mornings

So Lyla is finally sleeping through the night ever since we stopped breastfeeding. She used to wake up in the morning around 630-7, but it's been getting earlier and earlier. She's been getting up at 520 am lately.... Her room is completely dark, sound machine, etc. Any suggestions on how to get her to sleep in a bit later?? We put her to bed around 645 pm, I thought about pushing bedtime back to see if that makes a difference but the problem is she is always so tired by that time I think if we pushed it back she'd be over tired.