She was born in Belfast, the daughter of Dr. Joseph Stevenson Mulholland of Newry. She spent some years in a remote mountainous part of the West of Ireland after the death of her father. Her first novel was Dumana (1864), under the pen-name Ruth Murray. She originally wished to become a painter, but in her early literary life she received much help and encouragement from Charles Dickens, who highly valued her work as a writer and persuaded her to continue.

In 1891 she married John Thomas Gilbert, the Dublin antiquary and historian. They lived at Villa Nova, Blackrock, County Dublin. She became Lady Gilbert on his knighthood in 1897.

She produced a great number of novels and wrote a biography of her husband in 1905. She died in Dublin in 1921.