Hi Emil, In 1910 Nora Barnhart was living with her parents in Kiowa, Roger Mills Co., Oklahoma.
In 1920 she was living with her parents in Fawn Creek, Montgomery Co., Kansas.
According to the 1930 Choteau Creek, Charles Mix Co., South Dakota Census, she was married abt. 1924. Therefore, I'd look for her marriage license in Fawn Creek, Montgomery Co., Kansas. Also Robert and Lester Prater, Jr. were born in Kansas.
I found another Lester Prater and Nova Barnhart family tree on Ancestry and asked the owners to contact you.
If you don't know how to look for their marriage license, post an inquiry on the Montgomery Co., Kansas Message Board. Successful Searching!