And I agree with SoulfulSurvivor
What you're saying is that this woman should uproot her life and her child's life to chase after this man. The same man who ended the affair because she was married. Perhaps he came to his senses and realized that he doesn't want to be strung along waiting for her.
Also, if he was quick to get into a relationship with a married woman, well, history has a way of repeating itself. Somewhere down the road, if they do marry, he could well end up deciding to have yet another affair.
As for her---she was quick to have an affair instead of dealing with what's wrong with her marriage. Down the road when the passion wears off, will she repeat this behavior and have yet another affair? Would you advise her then to dump husband #2 and go after the next guy?
At some point, she needs to be responsible for her actions. She also needs to set a positive example for her child.
Yes, you are allowed to have an opinion, as are others, too.