In 1957, she married David H. Cogan, a wealthy Jewish businessman and inventor, and devoted herself to charitable and humanitarian causes here and abroad, serving on the boards of Hadassah, the Girls Clubs of America, and other nonprofit organizations.

[2] Following the Munich Pact which ceded the Sudetenland (part of Czechoslovakia) to Germany, Sharp and her husband (alongside many American Unitarians) felt that something must be done to give assistance to the victims of persecution.

The American Unitarian Association (AUA) raised funds, allowing the Sharps to travel to Prague on 4 February 1939 as representatives of the commission for service.

[2][7] Martha and Waitstill Sharp were recruited to work in Czechoslovakia, where a large community of Unitarians were present under the leadership of Norbert Capek.

[3] Later Martha and Waitstill recalled grave misgivings about leaving their children of seven and two, but they were convinced they would be well taken care of living with family friends inside the parsonage.

[2] On 14 March 1939, the Nazis were quickly advancing on Prague, but the Sharps decided to remain and continue their program, which was the most significant private American effort on behalf of endangered refugees in Czechoslovakia.

In Prague, the Sharps worked closely with members of the American Friends Service Committee (Quakers) to advance refugees' visa applications to Great Britain and elsewhere.

[5] On one occasion, Martha Sharp escorted 35 refugees, ranging from politicians to children whose parents had committed suicide, to Great Britain.

In May 1940, the president of the AUA, Frederick Eliot, and the USC's director, Robert Dexter, asked Martha and Waitstill to go to France as their "ambassadors extraordinary," to which the Sharps agreed.

From their base in Lisbon, Martha and Waitstill were able to help a number of Jewish children and several prominent intellectuals to escape Vichy France, including the German-Jewish novelist Lion Feuchtwanger.

Working with Donald and Helen Lowrie of the YMCA, Martha also provided assistance to the families of Czech soldiers who were stranded in France and were hoping to use a sea route for escape.

On 9 September 2005, Martha and Waitstill Sharp were named by the historical remembrance organization Yad Vashem as "Righteous Among the Nations", labeled as individuals who risked their lives to help Jews escape the Holocaust despite danger to themselves and others.