"född Nilsson" translates exactly like that -- "born Nilsson". But ...
Hilma is Nils's daughter -- patronymic "
Nilsdotter". Around that turn of the century, name customs were changing: patronymics out, family names in. Often, the family name was formed by "freezing" the patronymic. However, given the "supremacy of the male perspective" (to put it mildly ...) at the time, "Nilsdotter" was "impossible" -- so she got "Nilsson", instead. An alternative approach, in Hilmas situation, was to take fathers patronymic as family name. Sometimes a group of siblings ended up with a mix of family names, fathers patronymic, their own patronymic, frozen -- or a bright new, invented name ...
If you track her back, you may catch the name changing ...
