To be honest, I can relate to why she wouldnt tell you this, or why her husband might have asked her not to disclose the due date and gender. Honestly, it brings in a lot of unwanted questions, and unneeded prodding. If you tell people that your due date is XYZ, questions will start pouring in at least 2-3 weeks before that date (have you delivered yet?.. you look so big…you should have delivered by now), and even worse, should you happen to go beyond your due date! And all these queries are unwelcome, and not called for.
As for gender, it is kept a secret not because of any superstition, but primarily because gender determination is not an exact science during pregnancy. Ive seen and heard doctors go wrong many times.
I think one should just follow the dont ask dont tell policy in this regard.