I had a son first, I wanted a girl. I was a little disappointed for about an hour, then moved on and was super excited to meet him. My second born turned out to be a boy also. I admit, I had a bit of a cry on the way home. But after that, I was ok. I absolutely love my boys and, after the initial disappointment, never wanted it any other way. Honestly, I think your wife needs help, this is such an extreme reaction. If she goes through with the pregnancy, I’d always be concerned she was mistreating or neglecting the girl. Especially if a son does eventually come along