Dennett was born in Appleton near
Widnes in 1730. Her father Henry was a Protestant and her mother, Mary, was a Catholic. She was the last of their four children so when her father died when she was about five she was brought up as a catholic. In 1746 she went to the convent of the
Canonesses Regular of the Holy Sepulchre in Liege where her sister was already a nun. She was committed to a religious life and was said to have taken a vow of chastity when she was ten. Dennett was to young in 1746 to commit to becoming a nun so she was sent to gain an education at the school in Liege belonging to the Ursuline nuns. She knew that girls would come to the convent, but they would not want to become nuns. Dennett was determined that these girls would be educated wives and mothers. The school had always attracted English Catholic girls but the school's reputation meant that they attracted girls from many different countries. The school offered English, Maths and modern languages as well as wider ranging subjects including debating and double-entry book-keeping. ==Death and legacy==