I thought marriage was about sharing and compromise amongst other things, as are most relationships. She knew exactly what she was getting into before she married you, in relation to your child. So she has stated she is not ready to be a parent to your child, make it clear that you don't expect her to be a mother to your child as he already has one but that she should at least try and involve herself in his life, I mean she should naturally be interested him, he became a part of her immediate family when she agreed to marry you. How has she interacted with him before? I don't know, this is a tough one - you can take her statement as that of an unready and scared woman or that of a selfish one. She was aware of the entire situation from the word go so she has very little excuses for her behaviour.
I don't think you should be hasty with divorce. You need to discuss her reasoning further. I admit it is strange for you not to be living under the same roof with your wife, it is an extreme action on her part, try and figure out what she is apprehensive about, whether you can overcome these obstacles, however if she can ultimately never accept your son then your relationship is indefinitely doomed.
[SIGPIC][/SIGPIC]
Love is like a merry-go-round: you get all dizzy, and then you feel sick!