I'm sure your daughter is going to be THRILLED with her sweater coat! What a great use of your knitting talents!!
That being the case, though, remember that she's going to be growing and since I'm sure she'll love what you're making, you'll want to leave in some growing room for her. So when you measure for length for sleeves and the coat body, think about making the length longer than what will fit her right now.
Good luck with your project and please let us know how it's going!