Individual Details

Guesstimate for her birth is seen as 1782 - it was probably more like 1772 based on her marriage record.

Married name was Fisher according to John Irwin's will. There was a Tobias Fisher enumerated next to John Irwin in 1790 in Cumberland Co, PA. I found no Mary Fisher anywhere near the age she must have been in 1850 in Clermont Co; she probably did not live until 1850.

In fact on Google Books, I found the Record of Pennsylvania Marriages prior to 1810, Vol. 1, by John B. Linn, William H. Egle
"First Presbyterian Church, Carlisle"
p.476: 1789, April 2, Irwin, Polley and Tobias Fisher
If this her record she was born much likely around 1770-1774 - not in 1782.
There were two other marriages, same church records, for a Mary, or Polly Irwin
9 Feb 1797 - Mary Irwin married John Brown
26 Jun 1788 - Polley Irwin married Joseph McClellan
and
16 Feb 1792, Polley Irwine and Thomas McCartney
There were several marriages for the name "Irvine".

Birth	Abt 1772	Pennsylvania
Marriage	8 Apr 1789	Carlisle, Cumberland County, Pennsylvania - Living

Spouse

Living

Father	JOHN IRWIN (1751 - 1818)
Mother	ELEANOR [Irwin] ( - )
Sibling	John IRWIN (1780 - )
Sibling	ROBERT IRWIN (1787 - 1874)