I'll start with my praises first: I really like the language of the book. It certainly makes you feel like you're in a different world, maybe even time period, which fits the culty feel. I loved the names of the characters and they fit the story well and were super unique. Your writing style is good and I didn't see any grammatical errors or anything like that (at least that I noticed). The plot is interesting, maybe a bit slow at times, but original.
Read the story now
A few criticisms:
First, the disclaimer rubbed me the wrong way a little bit. As an agnostic, when I read it it felt like you were saying Christianity is the only truth in the world and it was very much geared towards not offending Christians... While kind of offending everyone else. I think since you describe them as a cult in the blurb people are going to assume the leader is full of shit (as cult leaders are) so I'm not sure if it's something you really need to include, especially since any non-Christian readers will be turned off by it. I almost didn't want to keep reading since it just left a sour taste in my mouth.
Secondly, I think some of your chapters are a bit long. That's not necessarily a bad thing, but on this platform, I think people are used to shorter chapters (2000-4000 words) so I'd maybe split up some of the longer ones. That's just me though, some people may like longer chaps
Lastly, I really really wish you would have started the book off with Selma totally believing everything the cult said. Based on my research of cults (I haven't dived in extensively, but I have read a lot/listened to a lot of podcasts about them) it takes a long long time for people to come out of the spell. There's a really famous example of The Seekers that psychologists wrote a book about called When Prophecy Fails where they coined the term cognitive dissonance. Essentially, a couple of researchers "joined" a UFO cult that believed aliens were coming on a certain day (some of the members included intelligent doctors, lawyers, normal people, etc) and then when the spaceship didn't come, they all kept believing the cult leader, even though she had been proved wrong. The psychological programming is REALLY strong in these types of cults, and usually members have to go through cult deprogramming therapy before they can recover from the ideals, and even that usually doesn't work. It's one of those things where once you're in, it's so so so hard to get out. This is for a couple of reasons: sunk cost fallacy, being born into the cult and that being all you know, being young and impressionable, fear tactics, starving/sleep deprivation strategies, using children/marriage against the person, using religious fear/sense of duty, etc etc. It's a really complicated phenomenon, and considering she grew up with it, something huge would have to happen for her to start doubting. I think it would have been cooler if you showed her 100% believing everything and then slowly starting to question (maybe after a large event?) and have her go back and forth and then she realizes it's a cult and wants to leave. I think that would be accurate to what really happens in cults. I would recommend reading about cults and the psychology behind it to better inform this, since I think that would make your already good plot even better and more engaging.
All in all, great job! Take my criticisms with a grain of salt since they're mostly my opinion not necessarily objective truths. Good luck!