The 1900 census shows Ellen Kennedy, born Jan 1865 in West Virginia and her mother Margaret O'Connor was born in Jan 1823 in Ireland and immigrated in 1846. They were living in Scottsdale, Westmoreland Co., PA.
The 1910 census shows the same Kennedy Family again in Scottsdale, but shows John as a widower (just so you know men are widowers and women are widows). Margaret is gone but sister-in-law Mary O'Conner 54 is living with them.
The 1870 census from Union Twp., Taylor Co., WV shows Margaret O'Conner 45, born in Ireland, Mary 14, born in MD, Maggie 13, born in MD, Patrick 13, born in MD (twins), Elle 6, born in Virginia. I could not find the family in the 1860 census anywhere under any spelling.
I suggest trying the Greensburg Family History Center, Greensburg Hempfield Area Library, Connellsville Area Historical Society and maybe the Westmoreland County Historical Society to see if they can help you in finding a death date, obituary and burial place. The Fayette County Genealogical Society might be able to help too.
Ella apparently died between 1900 and 1910 as her mother probably did as well. If they died before 1906 their deaths may have been recorded at the Westmoreland County Register of Wills. If they died after 1905 their deaths certificates would be with the PA Div. of Vital Records.