devil--really, start reading on "the best of" section here. You'll see a lot of people here are or were in your position. Just learn as much as possible and possibly learn from others here on how to speak with your daughter or rather "plant a seed of doubt" in her. But no matter what let her know you're going to be there for her (even if that's hard for you)....I say this because there may be some time where the JWs disappear during her time of need and this may be the one time you can step in.
Is your daughter baptized?