I guess everyone one forgets about the other X-Men films the first one, the second and third one.
When Mystique was captured after killing Bolivar Trask she escaped or was rescued she because was in X-Men, X-Men 2 and X-Men 3 which happen after Trask death but take place before for the Sentinel attack in the future.
The original timeline where the Sentinels created happens after the mutant cure is made and when Jean Grey becomes the Phoenix. Mystique is shoot with the cure saving Magneto in the third film the same film where Jean and Scott die. They are not in the future timeline so that means Mystique is a human in future timeline.
But like I said I don't think anyone remembers about number one, two and three.