A member of the Silent Sentinels, she picketed Woodrow Wilson's White House in support of women's suffrage in the United States.

As a member of the Silent Sentinels picketing Woodrow Wilson's White House for women's suffrage in the United States, she was arrested in February 1919 for her participation in a watchfire demonstration and sentenced to five days in jail.

[2] Mercer was honored for her sacrifices and in 1926 became a delegate to the Tenth Congress of the International Woman Suffrage Alliance in Paris, France.

[1] In addition to her activism,[3] Mercer toured Europe for two years and, upon returning to the United States, stayed at the Brunswick Hotel in Boston's Copley Square.

She would later purchase the landmark hotel and became its final owner and operator until the property was sold to IBM for their corporate headquarters.