It sounds like your daughter is already quite trapped mentally by it all. You do not want to ruin your relationship with her though if she does become a JW, so will need to be gentle with her.
You need to try to reason with her on thought provoking questions early on. She will be told not to believe apostate information, so say that since it is so important a decision she should at least research your questions. Unfortunately she may not care but want to be a JW to keep her husband happy.
Ask her who were Gods followers before Pastor Russell started the religion in the 1870's. Out of all the thousands of religions, why would he suddenly have this one? There is information about this teaching at http://jwfacts.com/index_files/5min.htm
An important difference in the JW New World Translation is that they have added the word Jehovah to the New Testament, changing the meaning of New Testament quite significantly. Ask if a religion that changes God's word the bible can be trusted.
Say that 1914 is very important to JWs but that the date for the start of it,607 is made up, with no historical evidence.
I find some of the many lies in the Watchtower to be eyeopening, such as their statements about earthquakes. Again, how can you trust such an org?
Discuss how much doctrine has been changed. Things like the wrong dates, that blood could be eaten, then not transfused at all, now most of it can be. There is a list at www.jwfacts.com
Hope that helps a bit.