Rynhart is born Jeanne Scuffil in Dublin on March 17, 1946, to Kathleen Connolly and Frederick Scuffil, a sign writer for the Guinness Brewery. She is an apprentice to George Collie RHA for two years and then attends the National College of Art and Design, graduating in 1969 before moving to Coventry, England, where she continues her studies in fine art and sets up a studio with sculptor John Letts. She returns to Ireland in 1981, moving to Ballylickey, near Bantry in County Cork, where she establishes the Rynhart Fine Art gallery and workshop with her husband, Derek.
One of the first bronze craft studios in Ireland, the Rynhart pieces include both small figurative cold cast bronze sculptures of flower sellers, fishermen, horses, sailing boats and musical instruments as well as bronze life-size statues, smelted in a foundry. Her busts of Oscar Wilde and Jonathan Swift are in the Dublin Writers Museum and a Rynhart bust of James Joyce is in New York Public Library.
Rynhart creates the Molly Malone statue for the 1988 Dublin Millennium celebrations. The statue is controversial at the time of its unveiling due to the statue’s revealing dress. Registrar of Aosdána, Adrian Munnelly, writes to the An Bord Fáilte criticising it. The statue is defended by the Lord Mayor of Dublin Ben Briscoe. Rynhart herself writes in The Irish Times that the clothing and appearance are accurate for women of that era. The statue has since become one of the most popular tourist attractions in Dublin and is fondly regarded by locals.
Rynhart also sculpts a statue commemorating the original Rose of Tralee, Mary O’Connor, which stands in Tralee Town Park. In 1993, she produces two statues in honour of Annie Moore, the first passenger processed through the Ellis Island immigration station on January 1, 1892. The statues are located at the Cobh Heritage Centre in Cork and Ellis Island in New York City. The Ellis Island statue is dedicated by the then-President of Ireland, Mary Robinson.
In 1994, Rynhart’s daughter Audrey joins the business. In 2010, Audrey and her husband, Les Elliott, take over the running of the business which is now based in their studio in Glengarriff, County Cork. From then onwards, Rynhart continues to do some modelling work but has largely retired.
Rynhart dies on June 9, 2020, aged 74, in Schull Community Hospital, Cork, following a short illness. She is buried in the Abbey Cemetery, Bantry, and is survived by her husband, Derek, daughter, Audrey, son, Barry, and grandchildren, Lydia and Sophie.