If Warren's 1/32 American Indian, then her mother would have been 1/16 American Indian. I find it extremely hard to believe that her father's family in Oklahoma (fka "Indian Territory") would have objected to his bride because one of her long-dead great-great grandparents was an American Indian.
http://www.breitbart.com/Big-Government/2012/06/01/Exclusive-Eloped-Elizabeth-Warren-Parents-Married-in-Religious-Ceremony