Eighteen year old Margaret (born abt 1828) arrived in New York on 29 August 1848 aboard the Sea King. There’s a Robert Oakman on the same ship – very probably her brother. Margaret went to live with sisters Eliza Oakman and Ann Oakman in Rensselaer (north of New York City).
In the 1855 Census we find Margaret living with her parents Walter and Eliza Oakman, along with her sisters Eliza, Anna and Jane, and brother Walter.
I’ve found no trace of her beyond 1855 – she may have married and therefore changed her surname.