Tread carefully, very carefully. Don't tell her anything diectly, as it will only put her on the defensive. It's better if you just ask her to help you understand something. Pick something small, not a major doctrine, something you might feel she might not automatically take the Watchtower s side. For example, if she loves children you could bring up the two witness rule when it comes to child abuse. Say that it bothers you that a child abuse victim might be asked to confront the abuser, and ask her if she feels the same.
You might wait until a situation presents itself, and have a few potential topics to talk about. Don't be confrontational, or show your disappointment if she did sent see your side right away. Drop it and wait for a better time.
This is all extremely difficult, but some have managed to get their spouse out with them, so it's possible.