Sonia Rachel Hopkins was born in August 1932, and worked as an occupational therapist. In 1965, she married William "Billy" McMahon, an aspiring politician in Sir Robert Menzies' government. She was 32, he 57. It was the first marriage for both of them. It surprised many that he married, as it had been widely rumoured that he was homosexual. He became prime minister in 1971.
Later that year, Sonia McMahon made world headlines after being photographed at the White House wearing a revealing dress in the company of her husband and United States president Richard Nixon. The white full-length dress featured see-through slits down both sides. The Washington Post described the dress as one of the most talked about items of clothing ever to be worn to the White House.
Their first two children were born before he became prime minister (Melinda; and Julian, who would later become famous as an actor in the United States.[1 ]). Their third child, Debra, was born in 1971, during Billy McMahon's term as prime minister.
As a prime ministerial spouse from March 1971 to December 1972, Sonia organised for a nanny to look after the children at the family home in the Sydney suburb of Bellevue Hill, while she lived with her husband at The Lodge in Canberra, attending official duties. In an interview with her biographer, Sonia McMahon said: "It was a hard decision. I loved being with Bill and I loved being a mum. But I knew I had to make a decision, and I chose to be with my husband."
Billy McMahon was knighted in 1977, and she became Lady McMahon, although she is generally referred to as simply Sonia McMahon. In the years following Billy's death in 1988, Sonia continued her socialite and charitable interests. She became a board member and patron of many charities, including the National Brain Foundation, the Sydney Children’s Hospital Foundation, the Australian Cancer Research Foundation, the Microsearch Foundation and Australia’s Sudden Infant Death Syndrome association.[1 ]
On 22 February 2009, Sonia McMahon was seriously injured after slipping on the stairs of a luxury pleasure boat owned by her friend, Paul Ramsay. She was taken to St Vincent's Hospital, Sydney suffering broken ribs, punctured lung, and multiple other bone fractures.