Mary is possibly the daughter of Richard Cammack of Corringham and Nettleham (1758-1826) and his wife Frances Palfremman. They were married in 1782 at Upton upon Kexby. His will (Stow Wills 1826/46) names his five children, including his daughter Mary and her four children. The doubt arises because he calls her Mary Cammack. I believe this is an error. The other possibility is that it is a duaghter in law but there is no suitable canditate in the family tree.I have more details of this family if your interested back to the 16th century.