Shall I register a child under 18 or wait till 18?

[tapash]

This is regarding my friend.
His letter from Home Office says the qualifying date for permanent residency is 13 September 2018. He has a daughter who is going to be 18 on 10 September 2019. Just wondering if his daughter can apply now to “register as British citizen”, or does she need to wait for a year just like her parents to apply for naturalisation? Plus when she is 18 she would have to apply for naturalisation with B1 and Life in the uk right? What is best to do avoid complications? Can someone help please? Thanks

[CR001]

Children born abroad can only apply when either parent is also applying or when either parent is already British.