It does sound like she simply might not need as much sleep as she used to. Does she show signs of being over tired? Is she waking up happy, or is she awake but cranky? Is she a fairly happy kid throughout the day, or does she get upset easily. Is she easy to get to bed at night, or is it a power struggle?
If she's not showing signs of being overtired, then she's probably getting enough sleep. Some kids don't need as much sleep as others. I know mine didn't need 12 to 13 hours of sleep at her age, no matter what the books said.
You might have to choose between a 7:30 bedtime and a 6:30 wake up time, because it sounds like you're not going to get both. If you do want her to sleep a bit later, I think you're going to have to keep her up a bit longer.
I hate to say it, but you're probably going to have to let her take the lead on this one. You can't make her sleep if she's not tired.
I agree that you don't need to worry about going to her and comforting her in the middle of the night. Ever had trouble sleeping at night? It happens to all of us. Sometimes I pick up my Nook and just read a bit. My husband will go to the living room and play his guitar. Maybe your daughter was just having trouble relaxing and going to sleep.
I truly believe that when child cries in the middle of the night and there doesn't appear to be a problem (sick, teething, hungry, etc) that they are really just saying, "Mommy, I need you. Don't leave me." Logically we know that they are fine and should just go to sleep, but when they are that little they don't see it that way. They really, really need Mommy.