Dependent Child over 18 moving to HK

Has anyone had experience in getting a dependent visa for a dependent child over 18?
Our daughter is moving to HK with us but under HK immigration law, once they are over 18 they are no longer considered a dependent. However she is still studying and will continue to do so once we return next year. We will obviously be looking after her and she will be living with us.
Any advice or experience in this is gratefully received.