Sarah was born in 1929, to Hayim and Zipporah Melumad. On her mother’s side, she was a sixth-generation descendant of aliyah by the Perushim, the great-granddaughter of Yoel Moshe Salomon, one of the founders of Nahalat Shiva and Petah Tikva. On her father’s side, she was a fourth-generation descendant of the Robinson family of Suwałki, Poland, the hometown of Yair. Her grandfather, Yaakov Melumad, was one of the first pharmacists in the Land of Israel. She was recruited for Lehi in 1946 at the recommendation of her brother David (Oded), who knew how fervently she wanted to dedicate her life to liberating the homeland. She was first involved in the youth division, putting up posters and disseminating promotional material. She then became supervisor of the youth cell and engaged in recruitment. In 1947, she met Matityahu Todi Peli, who was responsible for the youth division in the Lehi branch in Jerusalem. Eventually she would tie her life to him and build their family together.

That summer, the British intensified their attacks on the underground, and Sarah was captured putting up posters in the street. She was brought to the CID where she was harshly interrogated, but released.

After the Partition Plan was announced, Lehi decided to act against the Arabs. Lehi set up military camps, and Sarah was made the nurse of a combat unit. As the battles for the heart of Jerusalem began, on 5 Iyar 5708, Sarah found herself at the forward branch of the Hagana in the APC Bank neighborhood, representing Lehi. She witnessed a conversation between the Hagana commander in Jerusalem, David She’altiel, and the Lehi commander in Jerusalem, Yehoshua Zattler. Zattler asked for reinforcements to liberate the Old City before the Arab Legion could arrive. The next day, on Saturday, 6 Iyar, Sarah served in the combat unit, treating fighters wounded in the heavy shelling as they made their last attempt to break into the Old City. All of this was under heavy fire.

Sarah served in the Lehi camps until the Bernadotte assassination on 17.9.1948; then she was arrested and transferred to the Sheikh Munis jail. When she was released, she resumed her Lehi duties, serving as the contact for Dr. Eldad and Yitzhak Shamir, until 14/2/1949, when the first Knesset met.