I'm with Tracy P, who suggests an earlier bedtime.
With kids and sleeping, consistency and making sure they aren't sleep deprived is best.
Right now, my daughter wakes at 8:30am (like clockwork! I swear I could use her as an alarm). I have found that it works best to put her down to sleep at 1pm. She sleeps for 2hours. Then she goes to bed at 8pm.
If I mess with this at all, she doesn't go down well for her nap, and she doesn't go down well for night. She'll still wake at the same time in the morning, tho, which means she gets less sleep, and which means she gets off even more.
Try waking her in the morning at the same time everyday. Try putting her down for her nap and at night at the same time everyday.
OH! Another thing I've noticed: Now that my daughter is older and can walk/run, if my daughter doesn't get outside and isn't as active or doesn't interact with other kids enough, she doesn't get rid of her pent-up energy and doesn't go down as well because she's bored/not tired. I've found that making sure she spends lots of time playing with other kids or playing at a park/etc helps a lot.