Does it affect her nap if you keep her awake until it's due? Does she nap shorter because she is more tired due to waking early? If not, try to keep her nap at the usual time in order to try to keep her on track.
You are doing the right thing, if she isn't crying, leave her and go to her when you are ready to get her out of bed. Alex wakes at 6.45-7am and I have a shower before I get her, she is happy to stay there.