The Greene County Archives & Records Center, www.greenecountymo.org/archives/
might be able to validate her death date and where she died. I'd ask them if they look up obituaries too.
If they don't look up obits, you can contact the State Historical Society of Missouri, http://shs.umsystem.edu/newspaper/
who has the largest collection of newspaper on microfilm in the state. Successful Searching!