After the war, with no surviving family members, Karola decided to emigrate to Palestine, where she began going by the name Ruth. There, she lived on several kibbutzim, joined the Haganah, the underground military of pre-state Israel, and taught kindergarten, before moving to Paris, where she studied at the Sorbonne's Institute of Psychology. She subsequently went to the United States, where she enrolled at the New School for Social Research in New York and had her first child, Miriam. She married Manfred Westheimer in December of 1961 and they had a son, Joel.
Ruth received her Ed.D. from Columbia University and held a number of positions working in sex education and family planning before hosting her own radio show and several television shows. She has also authored more than 30 books and is an adjunct professor at Teachers College, Columbia University. Ruth and Manfred were together until his death in 1997. She has said that looking at her four grandchildren--Benjamin and Michal Leckie Westheimer and Ari and Leora (HS ‘14) Einleger -- reminds her that “Hitler lost and I won.”