From p. 90 of the short story “Beaded Soles” in Susan Power’s Roofwalker.
This part is about a girl who is “handsome” rather than pretty and delicate. She inherited a masculine body as well as the curse of being a Bull Head. It was Lieutenant Bull Head who shot and killed Sitting Bull, a prominent Lakota Native American who led others in resisting the U.S. government.
I think that when she mentions “long shadow of memory” she is referring to how her ancestor, Lieutenant Bull Head, betrayed the Native Americans by killing Sitting Bull. The fact that she is a Bull Head keeps other men from wanting her. Her unfortunate relation to the man who killed an iconic Native American figure makes her udesireable.