She was the second woman lawyer in Mandatory Palestine, after Freda Slutzkin[1]) and the first practicing female attorney in Israel.

During World War I, she stayed with her parents in Tel Aviv, but in 1917, she and Shlomo married in Switzerland and they moved to her father-in-law's house in London for four years.

She reapplied in 1924 with the help of the Union of Hebrew Women for Equal Rights in Eretz Israel, but was turned down again.

Horowitz submitted a petition on her behalf in December 1928 to the High Court of Justice as Rosa tried to influence the British authorities through her contacts and by using feminist arguments.

The debate on a draft ordinance regarding women practicing law in Palestine resumed, with Rosa representing herself before the High Court of Justice, a story that attracted international press attention.

[4] Authorities were at the same time hurrying to pass a draft ordinance from 1925 which was meant "to restrict women from appearing before Muslim, religious, and tribal courts and to bar them from various legal occupations.

She served as the Women's International Zionist Organization's (WIZO) first Honorary Secretary when it was founded in 1920, and continued her involvement after her return to Palestine in 1922.

She helped arrange permits for hundreds of Jewish refugees from Germany and across Europe to immigrate to Palestine.