I say and repeat, I have no patience with Nesta fans. I really do not have. I even feel tired.
Nesta's relationship with Feyre is not the normal sisterly relationship people try to pretend to be. Rhys has every right in the world not to like and not trust Nesta for the way she treats Feyre. Yet he'd always treated her before acosf (and Feyre's pregnancy) with polite coldness. But Nesta starts the acosf directly stepping into one of Feyre's traumas and Rhys knew how Feyre felt about that, how she felt guilty to the point of having nightmares about what the Hybern did to her sisters.
If it were the opposite, if it were someone disdaining one of Nesta's traumas, those same people would be the first to point the finger, as they already do. RHYS HAS EVERY RIGHT IN THE WORLD NOT TO LIKE OR NOT TRUST NESTA.
She never missed an opportunity to be an asshole to Feyre (or his friends) and she would just snap at anyone when she felt cornered. One example, not that Rhys was right, but the way Nesta tells Feyre about the pregnancy is just as wrong. She doesn't tell because she was worried, but because she was angry and wanted to hurt Feyre (which she's done her entire life).
You just can't trust overnight a person who USES ANYTHING against people, especially their trauma, when they're angry (and that was Amren's point to Rhys. "She can use it against us if she's upset ". Amren is not entirely wrong, however Nesta's main weapon is not a sword, but her words). So stop acting like Rhysand doesn't have a plausible reason for not liking Nesta or being uncomfortable with her.
Ah but he didn't want to tell her about the swords/magic. I won't say he was right either, but Rhys doesn't trust Nesta and he's not wrong about that either. Nesta has something very powerful in her hands that she spends the whole book repeating that she didn't care and that she didn't really know how to control it and that no one could quite understand what it was about. So tell me why should he just trust someone like that? Even so, he in the position of a leader reconsiders and leaves the decision to count or not in Feyre's hands.
So the first chance she gets to fuck up, Nesta does, telling Feyre about the pregnancy because she was pissed off. So tell me again where is he wrong not to trust someone like that after she's willingly promised him she won't tell? Rhys may have his share of mistakes in this book (and he does!), but not trusting Nesta initially is certainly not one of his faults.
If you think Rhys had no right to dislike Nesta because of Feyre (when he knew more than anyone how Feyre felt about Nesta), then you're an asshole who never loved, fought, or cared for anyone. Feyre NEVER had anyone to stand by her and defend her at any cost (including Nesta's abuse). Now she has Rhys.
To be clear: in the text I am defending the RHYSAND point of view. It's no use coming to tell me things that are not part of the character's point of view.