She has shown that telling her things won't work, so try more questions. When she says "JWs have the truth!" ask what she feels is the strongest evidence of that. if she is willing to respond and says xyz you could ask if she is aware of other religions that do or teach the same, as there is nothing unique about JWs.
Regarding divorce, it is hard to know just from your comments, but maybe she is insecure that leaving the Watchtower means you also want to leave her. She is going through a lot of inner turmoil and needs your comfort and reassurance that you love her and your beliefs are not affecting your desire to be with her.