I don't agree that what she is doing is ok at all. But they have been together for 4 weeks. How does he know she doesn't have an STI? Its a pretty big risk to take, to not be using a condom. I would want any new partner to be tested before I would be comfortable not using a condom.
But regardless of that, he should know if she is planning on using him to have a baby. I couldn't not say something if it was me. I haven't read all the posts here so I'm not sure if it's already been mentioned but has she thought about what life will be like for her and her child if she separates from this guy and then he decides he wants custody? Does handing her baby over for visitation every weekend fit in with her idea of what she expects parenthood to be like?