"That is her first child."
Translation:Dat is haar eerste kind.
Two reasons: Firstly, words like eerste, tweede, derde (first, second, third) etc. will always and on an e.
Secondly: only when a noun has the indefinite article een the adjactive will be without the -e. So: Het/haar mooie kind, een mooi kind. (mooi = beautiful). As I said, words like eerste do not follow this rule.
Well, apart from the fact that words like eerste, tweede, etc always end with e, the rule that e is not used with het words also applicable to cases when no article is present. I guess thats what the initial question wa referring to.
You need to break this section down into smaller components so it's easier to review. I've already reviewed twice with hardly any mistakes, and the progress bar is not updating correctly. Please fix this.