For the past few months, my girlfriend has been hanging out with a friend from work and her church group on the weekends. She says she has been learning a lot that has changed her views on things, but doesn't go into a lot of details. She says the things she has been taught would "sound crazy" if she told me because she isn't well versed enough to really back them up with evidence but that she is impressed with how much this church seems to have answers to questions. She also has not told her parents about these things. Strange, but no biggie. I try to be open minded about things as I am not religious at all, but I don't claim to have any big answers either about god or anything like that.
Tonight I found out she has some "special meeting" with someone important in the church. With further probing I found she is meeting with someone from Korea in the World Mission Society Church of God. I know very little about this group, but from what I can tell they are relatively culty and tend to aggressively recruit young vulnerable/lonely women going through a big life change. There are some past controversies with the group possibly being a doomsday cult, but idk how big that plays into their belief system really, they seem far less scary of a group than Scientology but something gives me the impression that they are manipulating her. I am already trying to tow a fine line of not pushing her away as we have been struggling with other relationship/mental health issues, but I really don't want to let her go deep down a rabbit hole here if it is something that is dangerous. FWIW, it also looks like this group does a decent amount of legitimate charity work.
Either go to a meeting with her, or get her to bring an existing friend to the meetings. I think involving a friend is probably the better option - if she's feeling cut off from people (relationship issues + cult recruitment makes it sound like she is), then bringing her friends into the solution will also address the underlying problem.
i.e. "Hey this place sounds really culty and I'm worried, can you bring Samantha with you to the next one of these?" Where Samantha is ideally her most hard-nosed anti-authoritarian friend.
This is a good way to build support against the cult. Make sure Samantha is on the same page about it being sketch though or she’ll also get roped into it.
Edit: just saw you mentioned going for the anti-authoritarian friend. Awesome.