Gatty was born in Burnham on Crouch, Essex, the daughter of Mary Frances (née Ryder) and the Rev. Alexander John Scott. Her father was a linguist, scholar and Royal Navy chaplain who served under Lord Nelson. Her mother died when she was young and Gatty took on a caring role in a family consisting of her father, grandfather and younger sister Horatia. She and her sister were educated at home, learning Italian and German, painting and writing poetry. Her poetry was encouraged by Margaret Holford but after a rejection by "Blackwood's Magazine" she did not pursue this further.