I’m not related to any member of this family.
1940 is the last available census at this time.
You either have mis-information or have have made a typo in your message.
You wrote - "I found her on the census from 1910-1940 and I have a marriage certificate reading 1890 31 Oct
Age: 10". 10 yr old girls don't get married !!!
Then you wrote - "I have her birth as Sept 1880 Joplin Missouri."
If she was born in 1880 then she would be 20 years older in 1900.
1940, 1930, 1920, 1910 - Myrtle Riggs [b. Mo, 1880] is not listed anywhere.
1880 - Myrtle Moffatt is not listed anywhere
WHERE did you find Myrtle - what state???