Surname is identified in the obituary of son, Harry S. Kelley.

According to LDS IGI records, her name was Martha Jane Simpson. If this is correct, could this be the correct person:
1850 Census, Jefferson Twp., Fayette Co., PA
Essington, James, 36, farmer, b. PA
Orpha, 33, b. PA
Cheyney, Orpha? (female), 59, b. PA
Simpson, Martha, 12, b. PA
William, 10, b. PA
Note: James & Orpha Essington were living with Martha and her husband, Joseph, in 1870.

1900 Census, Redstone Twp., Fayette Co., PA, June 12, 1900, p. 84A
Kelley, Martha, head, b. Sept. 1837, PA, 62, widowed, mother of 11 children, 10 surviving, parents b. PA
Wilmat, son, b. Aug. 1856, PA, 43, single, day laborer
Charles B., grandson, b. July 1880, PA, 19, single, day laborer

1910 Census, Redstone Twp., East & North of Nall? Road, Fayette Co., PA, April 18 & 19, 1910, p. 88
Kelley, Martha J., head, 72 widowed, mother of 10 children, 10 survive, housekeeper, b. PA, parents b. PA
Wilmont, son, 46, single, general laborer, b. PA, parents b. PA

Obituary, Daily Republican, March 5, 1917:

Martha Jane Kelly in her 84th year died this morning at the home of her son Searight Kelly in Frances avenue, First ward. Death was due to infirmities incident to advanced age. Funeral services will be held Wednesday afternoon at 1:30 o’clock from the Methodist church at Fairview with interment in the cemetery there. Several children survive.