In November 1897, she married the brewer Charles Conrad Nielsen (1866–1914) with whom she had five children Kaj (1898), Carl Wilhelm (1900), Erik (1902), Helmer (1905) and Inger Margrethe (1910).
[1] While still a child, she helped her father with his beer business as he experienced difficulties resulting from his drinking problems.
Nikoline Nielsen was involved in the company from the beginning and took it over when her husband died in 1914.
Further success was achieved in 1938 when deep drilling revealed a source of fine clear water in the subsoil, unmatched in the rest of Denmark.
As a result, the brewery gained a competitive advantage and was able to produce stronger beers.