Okay; the birth date didn't quite match but I don't know how much detail the person recording the burial would have known.
I have another entry for a Jane Christian, 73 years old, birth year abt 1798, burial date 24Jun1871, burial place Michael IOM, residence Douglas. In 1861 census, Jane and Wm were in Peel IOM. I don't find her in 1871 Census, taken April 2-3. Is it conceivable she was in Douglas but not counted two months before her death? You had earlier surmised she might have gone to England to live with a child, which would explain her being off-island in 1871. Did you have any piece of info pointing to that? Is there any other way to follow up on the 1871 burial date?
Thanks, Doug