OP - i have experienced the same dilemna as your wife. Been with my husband for 10 years and love him deeply. We have a very, however around 5 years ago I felt the strong need to have children. It was all consuming, all i could think about, and I did consider if leaving my husband was an option. For me it wasn't, but I can understand completely why others may choose to go.
You seem to be getting a bit of a bad rap here for being selfish by not giving your wife what she wants. I don't think you are being selfish, its just unfortunate that you don't want the same things in life, and there is no compromise to this - you can't have half a child! It is no one's fault!
But your attitude may be pushing her further away - you do sound very patronising when you are trying to suggest why she wants to be a mum. It is unkind of you to belittle your wifes feelings in this way. Perhaps you don't mean to, maybe it helps you to feel less guilty for not wanting the same things. My husband reacted in a similar way initailly, trying to suggest that my reasons were foolish, or not good enough. That is not your judgement to make, and will not change he mind. You both need to come at this from a non-blaming stance, neither of you are wrong in your feelings, you are just alienating her even more. You neede to just accept that she wants children, regardless of the reasons why. When my DH was able to take this stance, then we were able to talk things through rationally and work through our feelings together. It does sound as though your wife will probably leave anyway, but you owe it to each other to talk about things properly, Both showing sympathy and understanding to the other, not focusing on trying to change he mind.
If she did end up staying, or you agreed to have kids, it will not all be roses from here. Me and DH have had our moments, but for me the decision to stay with my loving husband was much more important than a possible child, and all that entails. I didn't want him to feel brow-beaten into having a child, because I believe that would be damaging to the child, and the marriage. I also ignored all the advice about having an 'accident'. i felt strongly that deceiving my DH in that way was a prertty disgusting thing to do. Mostly, things for us are really good, and i am happy with my choice, but only because we both show respect for the other's wishes and do not attribute blame or try to diminish each other's feelings... Only then can we support each other when things get bad.
I wish you and your wife well, and hope you can work things out. But whatever happens, you need to be honest and open about your feelings and really listen to her. Stop trying to get her to change her mind - just try to understand. If you can't show rspect for her views, your marriage is a good as dead anyway