With John Swift, Bobbie and Frank Edwards and others, she co-founded Ireland-USSR Society in October 1966.[3][4] She served as the society's assistant secretary.[1] She made the first of her 18 visits[2] to the USSR in 1968, and travelled the length of the country. She later described visiting the memorial to the 500,000 citizens who died during the siege of Leningrad as the most moving experience of her entire life. In 1973, while establishing diplomatic relations with the USSR, the then Minister for Foreign Affairs Garret FitzGerald lauded the society's work in developing a relationship between the two countries. Alongside the society's treasurer, Angela McQuillan, Harkin was seen as the society's driving force, seeing her elected chair in 1987. She was among the invited guests who attended the welcome of Chairman Mikhail Gorbachev to Shannon Airport by the Department of Foreign Affairs on 2 April 1989. On her 80th birthday in 1990, Harkin was given a presentation by Gennadi Uranov, the Soviet ambassador to Ireland. The Society's 21st anniversary commemorative publication featured articles from Michael D. Higgins and Theo Dorgan. After the fall of the Soviet Union, the Society decided to rename itself the Irish International Friendship Society, and Harkin and McQuillan established the Ireland-Russia Society. Both groups quickly waned.[1][3][4]
Harkin was a founding member of the Irish Anti-Apartheid Movement, and throughout the 1970s sat on the executive committee. She organised the sending of material support to prisoners and their families with Louise Parkinson, wife of Kader Asmal. She also worked as a volunteer with the Irish Family Planning Association in the 1970s and 1980s.[1][3][4]
She first met Peadar O'Donnell at age 13 when she delivered a note from her father to him during the Civil War. Following her husband's death, the pair re-established contact, with O'Donnell living with Harkin in her home, The Lodge, Monkstown, Dublin, from May 1979 until his death in 1986. O'Donnell was visited by many academics, journalists and activists, whom Harkin would host. In the 1994 reissue of The Irish Republican Congress revisited by Patrick Byrne, she contributed to the foreword. She died at Ashbury Nursing Home, Kill Avenue, Blackrock, County Dublin on 7 June 2012, and is buried in Deans Grange Cemetery.[1] Her son, Niall, is a sculptor.[2]