honestly i feel like even tho acosf didn’t give us the long awaited archeron sister hash out—it still answered why nesta preferred elain over feyre. acosf provided flashbacks of their mother literally grooming nesta into being a mini her and mama archeron clearly only saw elain as a valuable marriage asset. mama archeron trained nesta to believe that you can only love someone if they present as a marketable value to you or if they need you. while i do believe that nesta deep down loved elain for all those years, i also think that her severe protectiveness of her is rooted in the fact that elain was seen as marketable AND that elain is not like her at all. nesta couldn’t stand feyre because their personalities were too alike and feyre was a reflection of every insecurity and failure that nesta possessed. while on the other hand, elain was tolerant of nesta’s behavior and didn’t object to her cruelty at all, didn’t remind her of everything she hated about herself. nesta gave elain devotion and protection because her mother drilled it into her mind that elain NEEDED her since elain had “no ambitions or desires beyond eventually getting married.” this is why when they are forcibly turned fae, nesta takes elain’s trauma as a personal failure instead of acknowledging that this event happened to elain too. in nesta’s eyes and her mother’s mind, elain becoming fae is a loss because she can no longer marry graysen; which was the only thing they believed elain was capable of. this is why when, after the war, nesta is unable to maneuver her way around night court while elain can, she cuts elain off because she sees that elain doesn’t need her anymore—or even that she might’ve never needed her in the first place. nesta lashes out at elain, compares to a dog even, because she doesn’t know that love is not always a transaction. that’s why feyre being the first person that nesta says she loves is so significant. feyre is the first person who shows nesta that someone can still love you even if you give them nothing—even if you only give them hate.