(When I say that many people in the US don't care much about the Native American claims in Warren's campaign, I'm not saying that what she's doing is okay or a good thing. I'm just saying that the voters who care have little intention of voting for her.)
Just for the record, unlike deciding you're really the opposite sex, when it comes to race, you really can be, biologically, a little bit of another races or races. Most of us are. Cultural or social membership is another matter and gets determined by the group involved. The Cherokee have explicit methods for determining membership and Warren didn't meet the requirements.
As for voting for her, compared to what's left of what was a talented field, she's pretty much the only useful candidate. Biden has enough baggage for an old style movie star. Bernie is a non-starter. (The Repubs are going to have a field day, an absolute field day, running nonstop ads about his rape essays.) And all the rest of Rabbit's Friends and Relations are equally irrelevant. That said, I'm pretty sure nobody needs to worry about whether to vote for her. The way things look, she's not getting the nomination. So there's that.