It depends on the daughter in question as maturity is not dependant on age but on personality and upbringing, normally at that age she isnt really an adult and yet she is also not still a child, the problem comes with knowing when and how to treat them more adultly.
I have always gone with the idea that you should treat any child as maturely as they behave, and they should know that.
I know this answer is a bit vague and general but if you have any specific problems or areas that you wany advice on please post another question or e-mail me and I'll be more than happy to help you out as much as I can.
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