In the 1850 US Census, Ann Oakman, born Ireland about 1828, is living in the City of Troy, NY with Eliza Oakman (a sister?) and Margaret Oakman.
In the 1855 Census, Ann, Eliza, and Margaret are found living with their parents, Walter and Eliza Oakman, along with their brother Walter and another sister, Jane.
By the time of the 1860 Census, Ann is no longer to be found – it is possible she married and changed her name.