She is NOT a NBC; her mother was NOT an American citizen when she was born.
I rarely disagree with you, but, going on original intent the mothers citizenship is irrelevant. In the days of our founding the wife acquired the citizenship of the husband at the time of her marriage. A child also acquired the citizenship of the father even if born abroad. However language (law passed) was quickly added so as to preclude born abroad to be NBC. So IMHO Ivanka and all the other Trump children are NBCs (if they were born in the US or a Territory of the US).