"The child does not need her."
Translation:Het kind heeft haar niet nodig.
Firstly, hebben is an irregular verb, and the 3rd person singular is heeft.
Secondly, geen is basically the negative version of een and combines with nouns. Haar is a personal pronoun in this sentence, so you can't use geen, that would be like saying; The child needs no her.
(Actually haar means both her and hair, so "Het kind heeft geen haar nodig" is grammatical but means "the child needs no hair".)
Well nice question and the placement of 'niet' feels somewhat to be at the end( it's just that I've read it somewhere that niet goes at the end of the sentence) when you want to negate the whole idea about which the sentence speaks off.
But for sentences having hebben ...nodig, I also read it somewhere that nodig ( or some separable verbs) go at the end of the sentences no matter what and so at least for sentences with hebben...nodig and niet, this is what I've been doing. But we do need an expert on top of this, stat!