A person raised from birth in the JWs has all the cult beliefs stamped in their DNA. If they wake up to TTATT it takes years to deprogram. It's a huge battle to un-install the triggers even after the person is thinking for themselves somewhat. I was in my 30s when I first began studying with the jw and after being away from all of it for quite some time, I have emotional reactions to things and have to work through stuff all over again.
A person like that, who sees the big flaws in the WT, but is still emotionally attached to the way of cult life, may sincerely wish to change and believe that they have. But you cannot wave a magic wand and do away with a lifetime of programming. This lady has been programmed since birth. You are saying you want her to promise not to raise children you may have together in the cult. Even if she does promise that, and really believes that she means it sincerely, your children cannot escape the effects of what is in all the cells of her body and mind. They will take it in with mother's milk. They will absorb it because they are part of her, and the cult programming is wound around and throughout all her being.
If I was in your situation, and felt as if I was already committed to this relationship, I would have a vasectomy before seeing her one more time.
Breaking up is painful but facing reality and learning from others' experiences is the mature way to escape a lifetime of tragedy and sorrow. If you just can't break off from her then the next best thing is never to have any more children - and protect the ones you have from being influenced by this lady. She will not be able to help herself from hurting your kids' feelings. If they are involved with anything her comments will reflect her upbringing and tastes and sense of right and wrong. It will hurt your kids. You will constantly be torn between your loyalty to them and to her.
IF she was to see a professional for deprogramming, that would be a positive step. But I still would not have kids with her, ever. Get some nice pets instead. I admire you very much for seeking help in your decision-making.
Marina