It's a cult. They are using fear, obligation and guilt to maintain control over your daughter. Her being disfellowshipped does not help her break free because by engaging in conduct they have convinced her is sinful she has become too filled with guilt to think rationally. This is what they do and how they maintain control. I strongly urge you to read Freedom of Mind: Helping Loved Ones Leave Controlling People, Cults, and Beliefs (2012) by Steve Hassan.
I haven't yet read this book, but I have read his first book. He has had success in helping people break free of this thinking. Going on about the many faults of the Watchtower will not work, she has been trained to see this as an attack by Satan, it just causes her to become fearful. Steve first tries to engage with people on a personal level and reach their non cult personality by talking about their life before the cult, or their hopes and dreams before the cult thinking took over. He uses family members to reach out to them and remind them of those important relationships. Maybe you could try asking her what she would do with her life if she wasn't a Jehovah's Witness. You could ask her what she thinks about those who have given their life to the religion because they thought Armageddon was so close and who now have nothing. You know your daughter and what her thoughts might be, what might be potential issues.