Matilda was born in 1859. She passed away about 1901.
Sources
Daughter's death: "Idaho, U.S., Birth Records, 1861-1919, Stillbirth Index, 1905-1967", Idaho State Department of Health; Boise, Idaho; Idaho Birth Index, 1861-1919, Ancestry Sharing Link (free access) Ancestry Record 8973 #150064982 ($), Perl Letta Simmons born to John Boone Simmons and Matilda Jane Whitt on 13 May 1894 in Iowa, USA.
"Iowa, County Marriages, 1838-1934," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:KCWZ-JCT : 25 September 2017), Jno. B. Simmens and Matilda Whitt, 16 Oct 1878, Madison County, Iowa, United States; citing reference 217, county courthouses, Iowa; FHL microfilm 1,028,196.
Find a Grave, database and images (https://www.findagrave.com/memorial/125286620/matilda-jane-simmons : accessed 12 January 2022), memorial page for Matilda Jane Whitt Simmons (Aug 1859–1906), Find A Grave: Memorial #125286620, citing Twin Falls Cemetery, Twin Falls, Twin Falls County, Idaho, USA ; Maintained by ForeverRemembered (contributor 47279918) .