when I floated the idea in the past she was in jw mode and said that the secret book was bible based and others are based on the current system. Hoping she gets beyond that soon but who really knows.
JWs are not very good at compromise (mainly because having an open mind is only for people that are being studied with), f you went with the book "Men are from Mars, Women are from Venus", you can suggest she search it in the Watchtower Library to see if it is mentioned there (which it is, in a positive way. The article that mentions it actually uses the information in the book as the basis for the article). Considering this book and seeing that there is nothing scary in it, or that the worldly wisdom in it really wasn't bad, she might be a bit more open to other material. Alternatively, you could suggest that if a book does not violate bible principles, then there is nothing wrong with considering and weighing the information there. If it goes against bible principles, then you can stop reading it.
Good luck!