In 1930 (1930 US Census} and 1920 (1920 US Census), the parents you show for Madge were living in Council Bluffs, Pottawattamie, Iowa. Frank was born in Michigan and Cora in Missouri. Madge is not with the family.
According to the Iowa Marriage Index, Frank and Cora had other children:
Alvin E. Armstrong b. OK 1903, m. Ellen Maxine Hayden at Council Bluffs 23 Aug 1923
Louise Armstrong, b. Browington, Misouri 1905, m. Floyd H. Stevens at Council Bluffs 04 Apr 1925
On the 1910 US Census, Frank and his family, including Cora and 6 children (all b. Missouri) are living in Osage, Henry, Missouri. Madge is not with the family.
On the 1940 US Census, Cora, 64 b. MO, is a widowed mother-in-law living with Walter and Edra McAlexander in Clouncil Bluffs. This adds another child to Frank and Cora's family: Edra, b. Missouri ca. 1910.
Frank Vernon Armstrong apparently died in Council Bluffs on 1 Aug 1936. He is buried at the Memorial Park Cemetery, Council Bluffs, Pottawattamie County
Iowa. His Find-A-Grave memorial gives lots of info about the family, apparently from his obituary. It states that daughter Madge is Mrs. Baldwin of Drexel, Missouri.
I have added all this and other information to the profile I created, and I also created profiles for her parents.