Earthw7 says you canot say I am native and not know your family. In the sense that you cannot claim indian upbringing without knowing your family name (and tribe and totem etc) but you can certainly be of indian blood and know none of that. My wife's mother was adopted. She managed to obtain her mother's birth certificate. Father anglo name, mother Cree name, nationality listed as native. My wife had done enough research to think she was from the White Earth reserve. For years we would attend Sundance ceremony in N Dakota and spend the weeks after or before trying to find a roll with the mother's name on it. Without success. I would not have missed it for the world. After going as far as we could checking the paper trail, we would visit the elders to see if they remembered the name. Always a dead end but always the story of those who left this reserve and moved to that reserve or " you should talk to Joe X on another reserve. We drank endless cups of tea and spent hours talking to the most wonderful old folks you could hope to meet. However cold and challenging the officialdom was, the elders always threw open the door and in short order made us feel family. My wife finally gave up the search, too painful to get her hopes up and then crushed when the trail turned cold again. At best she is 1/4 blood but doesn't appear to have a drop of white in her. Which means she has suffered from the racism all natives are subject to without the support of tribe.
I bolded the section I am responding to. Does your wife's mother's birth certificate give adopted information, or is it original? If it lists her birth parents, with that she can look for them in census. An excellent free records search is:
https://familysearch.org/search She likely can find her people there and then work methodically back in time, through records. I'd be willing to help with online searches, just let me know. Full names and birth years, locations where people lived, can be a great start.
Maybe you've already done this, but just in case, I want to suggest doing the research work step by step, gathering all the records you can find. Then once you know for sure that there are Native ancestors, once you know their names and family details, then the relevant tribe can be looked to, along with the relevant rolls.
