Found some more clues.Futhey & Cope's History of Chester County says she was 'of Philadelphia'.
Also, I found some scraps in the family files that add some information:
* Sarah Gettys (b. 3-21-1774, d. 10-27-1816, m. John McDowell, 1-28-1796) * Jean Getteys (b. 11-21-1777, m. ? Oldham) * Mary Getteys (b. 1-23-1780, d. 2-27-1808, m. James Boyd) * James Getteys (b. 7-4-1783, d. 10-6-1813)