According to the 1880 census Anna Brita was working at the Woergaard estate (farm/dairy).
Hjoerring, Dronninglund, Voer, Woergaard, En Gaard, 46 (1), FT-1880, C6383:
Nicolaus Christhof Ruge 58, Married, Head;
Ernestine Louise Ruge, 45, Married, Wife;
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Anna Britta Andersdatter, 30, Unmarried, Servant, Sweden.
More than 20 were employed at the farm/diary, but I cut them out. The sister is not there.
http://www.voergaardslot.dk/english/Karsten