K.R.
I would say the opposite -- put her to bed earlier. All the sleep experts agree that the earlier you put a baby to bed, the later they sleep. It's because they are not overtired so they sleep better. Also make sure she is on a consistent nap schedule with a morning and afternoon nap that both last at least an hour. Most of her naps should be in a crib/pack n' play, not the car or any other moving device. After doing all that for 2 weeks and she's still waking up that early, then I would just let her cry until 6am so she knows that you're not coming in until then. Eventually she will just stay asleep, or at least stay quiet!
Resource: "Healthy Sleep Habits, Happy Child" by Dr. Weissbluth