So .. there doesn't seem to be any actual documentary evidence that 'Susan' was a daughter of Admiral Drury. However, Mary and Susan's brother, Captain Charles Chesshyre Drury (1799-1837) had a son, William Vallancey Drury (1821-92) who was the homoeopathic dentist who wrote an appreciation for Edward Cronin's obituary in the Homoeopathic World [March 1, 1882] p. 126, where he is described as 'a near relative of the deceased'.
There is a record for her death, https://churchrecords.irishgenealogy.ie/churchrecords/details/954f100500743
