Posthumous means born after the death of the father.

Ann appears to have remarried to Thomas Crellin.

1861, Ballaugh, district 3, schedule 20, Curragh
Thomas Crellin, head, married, 29, shoemaker, German
Ann, wife, maried, 37, Lezayre
James Stowell, son, 10, scholar, Lonan
Elizabeth Stowell, daughter, 8, scholar, Lonan
Catherine Stowell, daughter, 6, scholar, Michael
Isabella Crellin, daughter, 3, Ballaugh

Occupation of miller does not necessarily mean that he owned or rented a mill.
Probably was a journeyman who moved from job to job at various mills.