UNPOPULAR OPINION
First, it's important to remember that the Brotherhood of the Forgotten is a cult, a CULT. Many people tend to forget this, but it's incredibly revealing about how they recruit members (Adamai in this case) and how they manipulate others into adopting their ideology. A cult preys on vulnerable and destitute people. It's from this point onward that things get interesting.
Amalia is already fragile in season 3; she's being pressured into marriage, she's alone, her father is ill, and Sadida, who used to answer her prayers (in season 2?), no longer does. Add to that the fact that her only means of escape (the Brotherhood) has also become a source of tension and pain: between Yugo manipulating her emotions and Ruel/Sipho mistreating her : NOTHING WAS GOING WELL. She was alone, isolated by the Forgotten, and emotionally wounded. It's also worth noting that the worse things get/the more isolated she is at home, the more she become a spoiled princess, leading us to believe that these phases are actually defense mechanisms, either a way of coping with the selfishness she displays at times, or a way for her to signal, in a very clumsy way, that she feels bad, sad, etc., a bit like a child deliberately acting out to get attention from adults. We could assume a form of neglect during her childhood ( and it’s true “ we don’t was kind with her ” Armande world in season 1 ).
And that's where Sipho's actions and season 3 become truly disturbing. Sipho is Oropo and Echo's watchdog; he obeys their every command, is completely devoted to them. The moment when Sipho takes Ruel's place and hurls insults at Amalia takes on a much crueler turn, as I mentioned earlier. Amalia isn't a spoiled princess; she only acts like that when her situation is bad for her, or to serve the comic, nothing else. Basically, what Sipho told her was a huge "Shut up and ignore her emotions." And who benefits from that? The cult. Because saying nothing allows the person to be isolated as much as possible, to remain silent, and thus the process of control works. And that's why Amalia is behind everyone afterward (except when talking to Dathura). It gets even more disturbing because Sipho knocks her unconscious and places her at the Guru's feet like an object. I don't understand how the ENTIRE community accepted this as normal when it's so incredibly violent, especially with the kiss afterward, which wasn't even her choice (he initiated it, and she was ABSOLUTELY unable to resist). It's like real-life cults, women seen as sexual objects at the Guru's disposal, subjected to psychological and/or physical violence. What's craziest is that people hated Amalia for something she was the victim of. It was really from that moment that the community's misogyny was laid bare.
The season is interesting because of her character; it shows that she is weak, not physically, but psychologically unstable. It reveals that she has other, much more interesting flaws than "oh, she's a spoiled princess." She saw that she had the opportunity for a happy ending (her father no longer dying thanks to the new gods, the man she loves), and she fell into the trap because, after all, every cult promises you the best of all possible worlds.