In 1912 she married her first cousin (Reece Bernheimer[2] or Maurice Lowenstein[3] depending on the source.

[3] Returning to New York, Milner was active in the National Civil Liberties Bureau advocating for the rights of conscientious objectors to military service.

She would go on to serve as the executive secretary of the American Civil Liberties Union (ACLU) when it was formed in 1920.

Specifically, the ACLU forced the resignation of Harry F. Ward and Elizabeth Gurley Flynn.

Milner quit the organization in to protest the ACLU's advocacy for the rights of American fascist groups in the 1940s.