When you think deeper, Pome is insanely powerful. Her magic is capable of cursing four gods ( MT, WA, ML, Sugar Swan ) and two ancient heroes, maybe this is why she was the high priestess of Pomegranate Village. And perhaps she's interested in studying magic, judging from her impression of Kumiho " What a curious spell she uses... ".
Through out the story, Pome showed heavy devotion towards Dark Enchantress, it feels like everything she says and does is for Dark Enchantress. In CROB and CRK, Pome mentioned she would do anything for DE, even if she crumbles (dies). That was not an exageration, in CRK chapter 6, when Pome faced Gingergang, unlike Licorice Cookie and Dark Choco Cookie, who retreats after defeat, she stood there until she fell unconscious. And in Chapter 10, when she was defeated along with other Dark Cookies, she revived them with her spell. It seems like she is not the type of give up easily, imagine in the future she ends up in a life-threatening situation...
It is unknown what the thought process is which made her follow Dark Enchantress, did she betrayed her village just because she believed that's her future? My counter-arguement is that Pome is unlike Dark Choco, who also unwillingly became a part of darkness. Dark Choco was very depressed about his situation, while Pome was quite happy about being with DE, probably at the very moment she learnt the "truth". I would expect her to be more cynical if she were forced to join DE.
Other theory some people have is that Pome is brainwashed by magic. My counter-arguement is her attitude towards Matcha Cookie " The place beside Her is mine, not yours...! ", which seems to be a sign of jealousy. If DE were to brainwash a cookie to follow her, wouldn't jeolousy be a bit counterproductive?
I doubt it was because the priestesses disliked Pome as well. If you visit Pomegranate Village in chapter 5, and click on Priestess A, she seemed to be very hurt about Pome's betrayal, like she trusted Pome a lot. This shows the priestesses has good impression of Pome unless those hated Pome are killed.
One clue is that in this interview, it is said that DE saved Pome from suffering. Nothing about her backstory is said, but it implies Pome did not like how it was in her past.
In the map of chapter 5, the Pomegranate Village is located in a forest with lots of poisonous mushrooms, and in the artbook, it is said the path to this village is so rough, no cookies ever set foot there. Assuming those mushrooms weren't placed by Poison Mushroom Cookie, perhaps the life in this village is quite rough. Moreover, Pome seemed to relate to Starfruit Cookie when Starfruit mentioned being a leader is stressful, maybe Pome was telling the truth, being a high priestess at a young age is strefful to Pome.
Another thing that bothers me is the Sacred Pomegranate Tree seems to not do anything, ever. To be honest, majority of the legendaries in this series are quite useless or lazy or the one who's causing trouble. But if we compare this tree to Millennial Tree, he at least tried to protect the Churro Village and gave Churro Cookie powers, but the Sacred Pome Tree only stood there when Pome was destroying the place. Maybe Pome trusted the Tree fully, until she realised the Tree was not as reliable as the village believed, then decided to leave everything behind, feeling betrayed.
Perhaps the how DE convinced Pome to join her is through slow manipulation. DE is capable of using specters, tricking Gingergang into releasing her with the illusion of White Lily. By pretending to be White Lily, Pome assumed that was not the evil DE, but an innocent cookie. DE befriended Pome, maybe even comfort her while Pome was feeling stressed about the village. And when DE gained enough trust, she revealed that she was DE all along, casted an illusion in Pome's fortune-telling mirror, tricking her into believing that she was destined to join DE, and Pome accepted without a doubt.
Theory
There is a theory that one day Pome will be redeemed. In Sea Fairy Cookie's relationship chart, this is what she thinks about pome: " One day, Pomegranate will learn to fight her own fate... " This implies Pome might run away from DE, learning to live on her own. However, what if we got it wrong? The "fate" DE given to her is just an illusion, and the truth is that darkness will be defeated, when Pome realises this, instead of becoming good, Pome continues to fight for DE and the darkness, for DE is her everything. Maybe that is truly why Sea Fairy has tension with Pome.
I couldn't shake the feeling if DE is defeated in the future, Pome will be the next leader of Darkness. Pome seemed far mor cruel than DE ( well at least on screen, DE did have killed many soldiers during the Dark Flour War ), while DE was " saddled with unnecessary feelings /ref ", Pome suggested to get rid of Pure Vanilla Cookie as soon as possible. I'm not sure what would Pome do if DE gets redeemed, she might follow DE and become good also. However, in the scenario where DE dies, Pome might take DE's place in grief, becoming a successor far more villainous than DE.
