Kate may have been a distant cousin of Jefferson Davis. See the sources cited in her grandfather's Abraham Davis profile.
She married Joseph Pulitzer on 19 Jun 1878 in the District of Columbia. 
In 1880 she was living with her husband, Joseph and one year old son Ralph in the District of Columbia She was 24 and keeping house. 
Upon her husband Joseph's death in 1911 their estate was valued at $30.6 Million. This would have made them one of the richest families in the world at the time.
1900 US Census: Manhattan, New York, New York, on Seventy-Second Street. 
Joseph Pulitzer, head, 53, b. Feb 1847, Austria, (parents b. Austria) immigrated 1864
Kate Davis Pulitzer, spouse, 45, b. Jan 1855 in Washington T (town?), parents also born in Washington. She and Joseph married 21 years.
Ralph Pulitzer, son, 20 b. Jun 1879, New York
Joseph Pulitzer, son, 16, b. Nov 1883, New York
Edith Pulitzer, daughter, 13, b. Jun 1886, New York
Constance Pulitzer, daughter, 12, b. May 1888, New York
Baby Pulitzer, son, 3, b. Feb 1897, New York
17 persons living as servants, etc. in the household.
In 1910 she was living with her husband and four children in manhattan, New York City. 
Kate passed away 29 July 1927 in Deauville, Departement du Calvados, Basse-Normandie, France. Her body was returned to the United States and she is buried in Woodlawn Cemetery, Bronx, New York, Memorial ID 46257502. 
It is not clear when she was born. The 1880 Census record shows she was 24 at the time, which gives an estimated birth year 1856.  The 1900 Census, which recorded the month and year of birth, has Jan 1855.  In the 1910 Census, she is 55 with an estimate birth date of 1855.  Find-A-Gave with the photo of her tomb stone gives 9 January 1853.  Her obituary in Time Magazine said she was 78 when she died in July 1927. That indicates she was born in 1849.
↑ 1.01.11.2"United States Census, 1900," database with images, FamilySearch, accessed 29 March 2017 : Joseph Pulitzer, Borough of Manhattan, Election District 15 New York City Ward 29, New York County, New York, United States; citing enumeration district (ED) 785, sheet 1A, family 2, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,241,116.
↑ 2.02.12.2 Find a Grave, database and images, accessed 24 June 2020, memorial page for Kate Davis Pulitzer (9 Jan 1853–29 Jul 1927), Find A Grave: Memorial #46257502, citing Woodlawn Cemetery, Bronx, Bronx County, New York, USA ; Maintained by SLGMSD (contributor 46825959) .
↑"District of Columbia Marriages, 1811-1950," database with images, FamilySearch, 10 March 2018, accessed 24 June 2020 : Joseph Pulitzer and Kate Davis, 19 Jun 1878; citing p. 106, Records Office, Washington D.C.; FHL microfilm 2,107,965.
↑ 4.04.1"United States Census, 1880," database with images, FamilySearch, 16 August 2017, accessed 24 June 2020 : Kate Pulitzer in household of Joseph Pulitzer, St Louis, St Louis, Missouri, United States; citing enumeration district ED 139, sheet 181B, NARA microfilm publication T9 (Washington, D.C.: National Archives and Records Administration, n.d.), FHL microfilm 1,254,724.
↑ 5.05.1"United States Census, 1910," database with images, FamilySearch, accessed 25 June 2020 : Kate D Pulitzer in household of Joseph Pulitzer, Manhattan Ward 19, New York, New York, United States; citing enumeration district (ED) ED 1160, sheet 10A, family 175, NARA microfilm publication T624 (Washington D.C.: National Archives and Records Administration, 1982), roll 1043; FHL microfilm 1,375,056.