I don't think there is biblical evidence that she doubted Adam. She repeated to Satan (the serpent) the warning God had given Adam, but she added the word "touch," as in "not to touch" the fruit. Interesting addition, in that the word naga' -- translated "touch" -- can mean to apply something, in other words to apply knowledge. God did not forbid the "touching" of the tree of knowledge of good and evil, and in fact, applying the knowledge that there is, in fact, good and there is evil, is something we should do. However, in "eating" ('akai) we take something into us, allowing it to nourish us, become a part of us. In short, eating the fruit of the tree of knowledge of good and evil gave Adam and Eve the knowledge that there is pleasure go be found in doing evil. Simply having the knowledge that good and evil exist did not endanger their heretofore eternal lives, but taking that knowledge into them and acting on it, that is what "killed" them spiritually.