Elizabeth Grace Douglass born Dublin circa 1833

Elizabeth was the daughter of George Douglass and Grace Dunsford.  George, her father, was born in Scotland and, per family lore, had a military or political rank of some kind.  She immigrated along to New York in 1848, and shortly thereafter married Andrew Allen, who also was from Dublin.  Andrew died a few years later, of tuberculosis, after which ?elizabeth married my 2nd great grandfather, Robert Henry Mitchell.  I am trying to confirm Elizabeth's parents, and place and date of birth.  Also, looking for siblings, if any.