Werrenrath was born in Harrisburg, Pennsylvania, USA, on 28 January 1914. Her father, Charles Kisselman Imbrie, was a progressive Presbyterian minister who inspired her to lead a life dedicated to service and justice. He attended Princeton University, while her mother attended Vassar College. She attended Walnut Hill School for the Arts, an all-girls private boarding school in Natick, Massachusetts, graduating in 1931.

In 1937, she married Reinald Werrenrath Jr., and their engagement and wedding were announced in The New York Times. She met her husband while attending Wells College in Aurora, New York, during one of his visits to the college, where his sister also studied. He asked her to help him find a date. Reinald’s sister began listing potential candidates, and when Betty’s name came up, Reinald expressed interest. However, because she was a minister’s daughter, his sister at first assumed he wouldn’t be interested. She served as the president of her freshman class at Wells and was an athlete with a full scholarship, which also entailed working in the alumni office. She played field hockey, soccer, lacrosse, tennis, and golf. The couple moved to Forest Hills, New York, where she worked at the Metropolitan Museum of Art and her husband at NBC. He was then asked to move to Chicago to launch WBKB, which is now known as ABC-7, Chicago’s first commercially licensed television station.

In 1940, they moved to Hinman Avenue in Evanston, where their first child, Kirsten, was born in 1941. In 1942, her husband enlisted in the armed forces and attended Navy Officer Candidate School during World War II. During the war, she returned to New York with her daughter to live with her family. Following her husband’s military service, the family settled in Highland Park, where they lived for 53 years. Their two sons, Reinald and Peter, were born after this. Her husband resumed his television career, and both he and Betty became active members of the community, advocating for human rights and education. She volunteered with Meals on Wheels, collaborated with local churches on youth reading programs, and advocated for social justice and equality within and beyond their church community.

In 1998, the couple moved to a townhouse in Presbyterian Homes in Evanston. In 2018, her husband suffered a stroke at the age of 103. They moved to a new apartment in assisted living, but her husband passed away in August 2019 at the age of 104.

In February 2024, shortly after her 110th birthday, she was interviewed on the “Women Over 70: Aging Reimagined” Podcast.