My DS has never slept more than 10 hrs/night with a 2 hr (max!) nap during the day. He barely makes the minimum sleep requirements suggested, but that seems to be all he needs. For him, the afternoon nap is just not optional, for a couple of reasons: 1) he has to take one at school, and 2) even on the one or two days he's skipped the nap, he still doesn't sleep more than 10 hrs at night.
For your DD, I'd consider dropping the nap and see how she does. Many kids don't need 14 hours at this age, so I bet she'd be ok with 12 hrs/night.