Isabel Mary Grant Ussher was born in Dublin the only daughter of Richard J. Ussher of Cappagh House, Co. Waterford. Her mother died when she was a child and she was reared by a lady who ill-treated her which forced her at the age of 12 years to move to her aunt in Tunbridge Wells. Her aunt encouraged her to study art. She went to the Slade School of Fine Art in London and also attended the Academie Julian in Paris. Constance Gore-Booth was a pupil at the same time. Isabel moved back to Cappagh House to take care of her father. She had a studio there. Isabel specialised in pastels, sometimes painting in oils as well. She often copied old family portraits for her relatives. In 1901 she married William Odell and in 1908 they moved to Ardmore.

In 1915 they moved to Bristol. After William's death she moved to Suffolk in 1919. She started to paint landscapes and flower studies. She also painted in Norfolk. In 1925 and 1926 she painted a series of landscapes of the French and Italian Riverias. She settled with her daughter Mary in Welwyn Garden City Hertfordshire. In 1934 they returned to Ardmore and built a house and studio there. In 1924 Isabel and her daughter held a joint exhibition at the Country Shop in Dublin. Isabel showed landscapes from Co. Waterford and Connemara. One of the pictures was a portrait of Tom Murray the ploughman who worked on the Cappagh estate. This picture is reproduced in her nephew Arland Ussher's book "Caint an tSean-Shaoghail" published in 1942. The picture is now in the Waterford Municipal Collection. Isabel died in 1948.