Actually, if you listen to the DVD commentary on Restless (end season 4), you'll hear Joss say that the character of Dawn was originally written as eight or nine years of age. When you realize that, then she makes sense, sort of (although, couldn't they rewrite her dialogue at least?)

I'm taking the idea in this that while the monks may have given Dawn 14 years of memories, her social skills and coordination were bad because she didn't have the experience. Carry that down the line to 5, and she's a little more in the age group she should be, with coordination and all that.

More on this later. I'm at work wasting time but I did want to respond to this as soon as I could.