There is one ancestry.com tree that claims her unmarried name was Cantrell, and that also claims she had been married to a Harold H Stapleton (1908 - 1961)

SSDI:
Margaret I Barnes, born 14 Aug 1916, died 21 Nov 2008 in Turner, Marion, Oregon

1930 CENSUS, SALIDA, CHAFFEE, COLORADO:
Margaret Cantrill, age 13, is listed as “step daughter” in household of Elbridge L Samson and his wife Odessa I Samson. Age at first marriage suggests Elbridge married Odessa in 1926. However Odessa was first married about 1916.

1940 CENSUS, SALIDA, CHAFFEE, COLORADO:
Margaret Cantrell, age 23 born in Colorado, is in household of Ina Samson, age 42. Ina and Margaret are both reported as “Divorced”. (The above Harold Stapleton is in the same city, marked “M” (married), but the “M” has been scratched out. So it is quite possible that Margaret married and divorced him between 1930 and 1940. Also I am guessing the Margaret’s middle name was “Ina”, after her mother.)