Sybil was the wife of D A Thomas, Liberal MP for Merthyr Boroughs from 1888-1910, later the first Viscount Rhondda and a prominent industrialist. Her daughter was the feminist Margaret Haig Thomas. As President of the Welsh Union of Women’s Liberal Associations Sybil made a significant contribution to the Liberal women’s organization in Wales. She sponsored the women’s suffrage movement, entertaining Mrs Pankhurst at Llanwern. During the First World War she chaired the Women’s Advisory committee on National Savings and supported her husband in his role as food controller and was created a Dame for war services. In addition she played a key role in encouraging her daughter’s feminist and suffragist values so helping shape her daughter’s career.