Hi David,
My great-great-great-grandmother was born Elizabeth Anderson in 1801 in India. She married Thomas Cox, Aug 23 1822 in Travancore, India. He died Nov 23 1851 in Castletown, Isle of Man. Is it possible that the Elizabeth Anderson that you're inquiring about is the same person and that as a widow married your great-grandfather William? She would have been 50 at the time. My ggggrandma died in 1866, in Douglas, Isle of Man.