Crosby worked closely with John Wesley (June 17^th) and, although mainly working in the North of England, preaching until the day she died, she travelled extensively across Cornwall with Wesley.

Uninterested in religion until she was fourteen when she began attending her local Anglican Church as a family duty, she became terrified of death after becoming seriously ill at the age of seventeen and, convinced that she would go to Hell, she became a committed Christian. 

In the winter of 1749, she heard both George Whitefield and John Wesley preach and became a committed Methodist.  At around the same time she met some other Methodist preachers and found her lifelong vocation preaching and working with Mary Bosanquet, Sarah Ryan, and Mary Clark to assist the disabled and the poor.

John Wesley had a short-lived marriage to  Mary Vazeille and it has been suggested that Wesley’s wife became suspicious of Crosby’s intentions towards John when she accompanied John Wesley across Cornwall in 1758.