Mary is listed in the Isaac Mumma Family bible as Polly Hoffer.
http://www.mumma.org/archives/bible1.html
. A Polly Hoffer, wife of Joseph Hoffer, is identifed in Christian Mumma's Will and this entry in the 1850-70 census is a perfect fit to be his daughter. There is confusion regarding her birth date. The census records suggest a birth year of about 1814 or 1815, yet her tombstone show 1813
https://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=86294902
The family is also listed in the "History of Frederick County, MD, Williams history of Frederick" Biographical records under JACOB H. GORMAN. The surname is mispelled as HUFFER instead of HOFFER
1850 Census, Conewago, Dauphin, Pennsylvania,
Household Gender Age Birthplace
Joseph Hoffer M 33 Pennsylvania
Mary Hoffer F 33 Pennsylvania
Fanny Hoffer F 9 Pennsylvania
Elizabeth Hoffer F 7 Pennsylvania
Cyrus Hoffer M 6 Pennsylvania
Mary Hoffer F 4 Pennsylvania
Isaac Cayler M 18 Pennsylvania
Sarah Andrews F 17 Pennsylvania
1860 Census, Lower Swatara Township, Dauphin, PA
Household Gender Age Birthplace
Joseph Hoffer M 44 Pennsylvania
Mary Hoffer F 44 Pennsylvania
Elizabeth Hoffer F 16 Pennsylvania
Cyrus Hoffer M 15 Pennsylvania
Mary Hoffer F 14 Pennsylvania
Aaron Hoffer M 9 Pennsylvania
1870 Census, Hummelstown, Derry Twp., Dauphin Co., PA
Household Gender Age Birthplace
Joseph Hoffer M 53 Pennsylvania
Mary Hoffer F 55 Pennsylvania
Elizabeth Hoffer F 25 Pennsylvania
Cyrus Hoffer M 23 Pennsylvania
Mary Hoffer F 22 Pennsylvania
Aaron Hoffer M 19 Pennsylvania