Thinking about leaving a girlfriend who is the mother of OP's child sounds not just insulting, but even disgusting. It sounds like OP did not advance enough. I might be wrong, but for me it seems that leaving a girlfriend for not joining Zevism is equivalent to forcing her to join which goes against the Satanic Ethics.
She might be avoidant in joining due to the following reasons. She might be unready. Also, maybe she finds OP's pushing too intimidating and forceful which strengthens her subconscious indoctrinated belief that "Satan is bad" which also goes against Satanic Ethics. OP by leaving her would strengthen this belief and leave the woman devastated.
If the relationship is adequate, if the girlfriend behaves well in other areas, there are no untolerable problems with intimacy, then leaving her would be inadequate, basically a betrayal. Breaking up can be tolerated if and only if there is no way to improve the relationship, and everything to improve it has been done, but the results were not satisfactory for both parties. In other words, people break up when they believe that by breaking up they are going to have a better life. Otherwise, people should try to improve their relationship. Love is not something that is freely given just for you polluting the airwaves. It must be built over time with mutual effort, and sometimes it might be extremely hard.
Solution here is simple. First, one needs to stop using Zevism as a scapegoat. Secondly, a person needs to take care of his child, be a good father to him/her, and make sure the practices of Zevism would not be used to avoid responsibilities towards one's own child. Finally, one can find a calm place/room for the practices.
To summarize, OP should not ask what to do with his girlfriend. He should ask what to do with himself first. I can not see anything wrong with his girlfriend.