There are some real inconsistancies in Margaret's application...it appears she list some of Robert and Nancy's children (who is related to Charity Powell her "Indian" grandmother) but then lists Jonathan McGinty as her father and a Deby as his wife (and he was not married to a wife named Deby. Liza who died in 1869 WAS Jonathan's daughter but that would make her Margaret's couin, not sister. And Couch's did not have children named Ben, Carroll or Mary.
So it is a big mystery and the application mistakes may have been what led to her being rejected the Indian status she wanted. I have heard that Charity Powell Couch told people that she was part Cherokee but there is no proof.
Robert and Nancy may have been married in MS. as that is where they migrated from whith Robert's father, Joseph and his brother Joseph, Jr. (JJ) and Jonathan.