"Reverend Angie," Junko says, with a smile on her face and ice in her eyes. "Take my confession." (Proceeds to confess to extremely personal and/or graphic things while Angie keeps smiling and refuses to be baited.)

The vibe is, Junko is running a despair church, and obviously the Remnants are the congregation, and Angie shows up and she's still Angie, so she still has her quirks and flaws, but obviously going to Junko's despair church and seeing what a bad influence Junko is on everyone, she's trying to guide them down a different path.

Junko's fanaticism is messier and more cathartic, and Angie's maybe-fanaticism is more tidy and sanctimonious.

Some of the members defect from Junko's way to Angie's way. (Mahiru and Hiyoko are split along these lines, with Hiyoko siding with Junko and Mahiru siding with Angie.) (Nekomaru definitely defects to Angie.) (Nagito likes Angie but doesn't commit to either side completely.) Junko and Angie are very civil to each other, while fighting this ideological battle via their congregants.

And they kiss in Angie's prayer closet after Angie finds Junko hiding in there to spy on her.

Izuru is, like, a groundskeeper who also doesn't take sides.

(And also Makoto runs a cafe in town (Oops, barista Makoto is back?), and Junko has banned her congregation from visiting the cafe so they can't find a community anywhere else, but not everyone obeys. It's a whole dramatic secret.)

Specifically, imagining if Angie and Junko were both at Hope's Peak at the same time. Angie being almost the only one who knows what Junko's up to.

If we're taking in-game characterization at face value, maybe they're both starting different ideological/spiritual movements at the same time. They cross paths every now and then, and Angie's like, "You won't win, you know~. God has chosen this school to be a place of good, not evil. 😊"

Junko could play coy, but first of all if we're counting the anime as canon it seems like she was pretty much never not being obviously evil, and second of all even if we're not counting the anime as canon I could see her making the calculation that she has nothing to lose engaging with Angie semi-honestly, if they're alone. So maybe she goes, "You think everyone you sway to your side believes in the same idea of good and evil as you? How naive. As long as you teach them not to think for themselves, you're priming them for me. You think you're taking them out of play, but really you're just making them more vulnerable."

Angie giggles. "You're so silly, senpai! Angie never told anyone not to think for themselves." With a joyous but penetrating gaze, she continues, "If your goal is to hate yourself half as much as God loves you, you'll never succeed, you know!"

Junko could go a lot of ways; she could go Sad Mode and say, "I wish I could hate myself. A feeling like that might be kind of exciting." Or she might go Cute Mode and say, "Aww! I've never had an underclassman try to psychoanalyze me before!" Or neither of those. Honestly, I'm writing this post mostly because I'm trying to brainstorm how Junko might react to Angie, on the premise that she doesn't just blow her off as insignificant. Both Junko and Angie are characterized as extremely competent at seeing a person's innermost wants and vulnerabilities. It would be cool to have them see through each other. (Though of course, obligatory "But Angie didn't see through [so-and-so]," and arguably the same for Junko.)

My very first thought was of someone like Mukuro asking Junko, "Is Yonaga creating her own cult a problem for us?"

And Junko sarcastically going, "Oh you're right, how can I possibly sow corruption into an extreme religious movement?"

But it's fully reasonable to say that outside of a killing game Angie just kind of wouldn't start a cult because she wouldn't feel threatened enough to do that. I view Angie as a cult survivor who exhibited cult behaviors in the killing game because she didn't know another way to express her fear without interpreting it as a lack of faith, so a more healing version of her school days would have her unlearning some of the stuff the was raised with (And, if I were keeping with my own personal headcanons, beginning to engage with her own culture outside the paradigm of the cult that appropriated it.) and being able to identify the threat of despair earlier than some because she knows what to look for.