He asked her to do the testing, she did it, the doctor the had her passing it and analysed the results specifically said the results show she had a native america among her ancestors. So by the very standarts Trump choosed, she says the truth when she pretends to be a descendant of native americans.
True, the Cherokee Nation refers to different standarts, they require you to have an ancestor appearing on the Dawes Rolls. But Trump did not asked her to name which of her ancestors appears on the Dawes Rolls, he asked her to go through DNA testing, which she did.
He asked her to prove her claim, he choosed the method she would use. She accepted, went throught the medthod he had chosen and the results were conclusive. So now Trump is trying to pretend he's gonna refer to different standarts, standarts he knows she won't meet.