I recognize your concern and one night per month isn't very long is it Agnosticnow? But rather than worrying about the future relationship, would it not be best to make sure you have a good welcoming, close and loving relationship now?
Of course you are concerned about losing her to the JW cult, while that is quite understandable, the main concern surely is the long term welfare of your daughter, not your needy relationship with her later on? Believe me I do understand as I have two JW children.
For her to flourish as an adult she needs to be loved, confident, kind, educated and able to think straight. Can she see these things in you?
Without overtly instructing her you might awaken her curiosity, you can leave a trail of ideas over the years, which she might want to find an answer to by herself. One might be the antiquity of humankind. The archaeology shows us to be at least 150,000 years old with the understanding that we were also here a very long time before that. Get her to think about Neanderthals, how on earth does that fit in with (fairy) tales such as Adam and Eve? Leave open questions about the stories in the Bible; are they folk tales or true historical accounts? (The flood is laughable, and scholarship has shown there was no literal Biblical exodus of Jews from Egypt.)
Encourage her personal growth otherwise the JW org will stamp her down... and always encourage her education including discussing school matters with her if you feel comfortable with that.
The main thing though is that she gets your complete love and that she grows up a confident woman knowing that her real mother (at least) loves her unconditionally. From that secure platform she will be better able to make good decisions on religion and family.