This Missouri Johnson is in the correct location in the census data. Maybe you can find more records by tracing the listed parents. In the 1900 census, if you look at the actual census image, this Missouri and her parents James JR & Lizzie are living in the same house as another James Johnston and his family, who by ages listed, may be her grand parents, and another household of John Johnston -? uncle.
There is a Morgan Johnston, son of James Johnston and Elizabeth Michaels who married a daughter of Sidney Rushworth. of the correct age to be Missoura's brother however on his marriage cert he is listed as 'white' while on other records the family is listed as 'black.?
U S Census, 1900 Winton borough, Lackawanna, PA
Citing this Record: "United States Census, 1900," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/M338-YTX
Head James Johnston Jr. M 40 PA
Wife Liza Johnston F 27 PA
Dau Sarah Johnston F 6 PA
Son Morgan Johnston M 4 PA
Dau Missoura Johnston F 1 PA
Census image here: Shows James Johnston Sr. as well, in same house.
https://familysearch.org/pal:/MM9.3.1/TH-267-11108-170713-28?cc=1325221&wc=M94B-JBH:n476420499
U S Census, 1910 Winton Ward 1, Lackawanna, PA
Citing this Record: "United States Census, 1910," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MG4F-8BM
Head James F Johnson M 51 Pennsylvania
Wife Lizzie Johnson F 36 Pennsylvania
Dau Sarah Johnson F 16 Pennsylvania
Son Morgan Johnson M 13 Pennsylvania
Son Missouri Johnson M 10 Pennsylvania
Son James Johnson M 8 Pennsylvania
Son Thomas Johnson M 6 Pennsylvania
Dau Elizabeth Johnson F 3 Pennsylvania
Pennsylvania, County Marriages, 1885-1950
Citing this Record: "Pennsylvania, County Marriages, 1885-1950," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/VF78-VL6
Name: Morgan W. Johnston
Marriage 11 May 1936 Place: Peckville, Lackawanna, PA
Age: 39 Birth (Est): 1897
Father James Johnston Birth Moscow, PA
Mother Elizabeth Michaels
Spouse Alice Michaels
Birth (Est): 1892
Father Sidney Rushworth Birth Eng
Mother Evelyn Walbran Birth Eng