Thomas, daughter of a shipowner, was born at Croydon, Surrey, England, probably between 1840 and 1845. She was brought to Australia by her parents in 1852 and later on studied sculpture under Charles Summers at Melbourne. She exhibited a medallion portrait at the first exhibition of the Victorian Society of Fine Arts held in 1857, and 10 years later went to Europe to continue her studies. She had a medallion shown at the Royal Academy exhibition of 1868; after studying for three years at Rome she obtained a studentship at the Royal Academy, London, and in 1872 won the silver medal for sculpture.
Between 1873 and 1877 ten of her paintings, mostly portraits, were hung at exhibitions of the Royal Academy. In 1880 Thomas wrote a memoir of Summers, her first master, A Hero of the Workshop, and in the same year completed a bust of him for the shire hall, Taunton. She afterwards did busts of Henry Fielding and other distinguished Somersetshire men for the same place. She began contributing verse to periodicals and in 1888 Douglas Sladen included seven of her poems in his Australian Poets. Miss Thomas subsequently wrote several books of which A Scamper through Spain and Tangier (1892), and Two Years in Palestine and Syria (1899), were illustrated by the author. In 1902 appeared an interesting little book, Denmark Past and Present, which was followed by How to Judge Pictures (1906), and a collection of her verse, A Painter's Pastime (1908). In 1911 appeared what was possibly her most valuable piece of work, How to Understand Sculpture. Another volume of verse, Friendship, Poems in Memoriam, was published in 1927. She also did a large number of illustrations in colour for From Damascus to Palmyra, by John Kelman, published in 1908. She died on 24 December 1929.
Thomas is also believed to have painted a number of middle eastern watercolours with a curious monogram consisting of an inverted L or Greek gamma over a gothic M