What time is she going to bed??
What are you feeding her? Apples, apple juice, and apple sauce will all give a child (or you) more energy than a cup of coffee. (Or are you giving her lots of sugar??) Something to think about.
Also, how do you put her to bed?? Is there a regular routine?
Do you look her in the eyes when you speak to her? Are you perhaps asking instead of kindly but firmly telling? Is there something to her routine elsewhere that't not taking place at home??
As for the actual length of time she sleeps: They do go through phases where they don't sleep as much. During growth spurts, they will sleep long periods, and when they're not growing as much, they will sleep shorter periods of time.
A last thought--she may simply be wanting to be with you more. My oldest child (now 17) had to be in daycare, and she was always very needy and afraid I was going to leave her. On wknds, she would wake up very early just because she wanted to see me as much as possible. She nay not be able to articulate that to you or herself, but that may well be the case.
Just love on her lots and set firm boundaries and loving discipline to make her feel safe. She will be grown and gone before you know it,and you will MISS THIS!! Believe it or not!
Blessings,
H.