Could you tell us a little more about what you are looking to find?
What information do you have already?

Do you know where (State/county) she may have died? If so, have you looked for a death record? Do you know where her children lived in 'later' years?

Patsy married Mingo in East Carroll in 1875. She was found in the 1900 and 1910 East Carroll parish, LA, census.

In 1920, a Patsy and Charles Johnson were just across the border from East Carroll, in Arkansas. Was this your Patsy? A Charles Johnson is listed in the Arkansas Death Index for 1920. There is also a 'Charley' Johnson listed in 1928 - both before the 1930 census.

Long Shot:
In 1930, there was a 'Patsy Johnson', living with a 'Maggie Allen' in Pointe Coupee parish, LA. She was born in LA (ca. 1859), and was listed as 'Mother'. Don't know if this is the same 'Patsy' who married Mingo Kennedy and Charles Johnson, however.
Note that Patsy has a daughter named Maggie, who was listed with her siblings in 1900.