I have researched critical thinking and I am going to try to instill that in her whenever possible
I think that is the most important thing you can do, as cults train people to be able to think only in term of black and white. My situation is somewhat different as I live with my step daughter, but her way of thinking is probably similar. My step daughter was very upset when she first was told by her study conductor that God was going to kill me at Armageddon because I no longer believed the Truth. She was about 10 at the time, she is 14 now. However over time I let her know bits of what I knew, and she rapidly realised that the reasoning of JWs does not make sense.
Things that made her think were questions such as whether God would want to kill all her school friends because they were born into other religions. 1 thing that shocked her was that the Watchtower only started in the 1800s by a man called Pastor Russell, she assumed JWs always existed. Also information that lots of religions say they are the truth, and only they will be saved, religions such as Christadelphians, Mormons, Scientolgists. The children in those religions think that everyone else wil be killed by God, so who is right? There is information about similar religions at http://jwfacts.com/index_files/similar.htm that may help you. Questions like that can lead her to the conclusion that God loves everyone that tries to worship him.
The other thing is to be a really nice Mum. The more she loves you the more she will trust your reasoning.