I think one of the things that makes Feyre more easily stomached than some other protagonists in her vein is that in spite of her drastic circumstances, she doesn't claim to immediately be an expoert- and she isn't a natural at everything. Maybe the universe threw an abnormal amount of power her way in an unnatural span of time, but she has to actually learn to wield it. That's at least more bearable than the very common alternative
Let's not mistake this for when she's playing tough, because we all know sometimes that leads to decisions that has us shaking our heads and asking 'why?'/ But she is strong. As much as we all love Nesta and Elain now, the truth of the matter is that she grew up in a situation she should not have survived. She was a child that had to provide for herself, and when it mattered she kept her wits about her and fought tooth and nail not only for herself, but for them. She puts the people she loves before herself and she fights for them at her own expense, which is the truest strength of all.
Here's the thing- in spite of all the crazy, insane things that Feyre Archeron has going for her, she's somehow relatable enough that most of use find ourselves living vicariously through her... and liking it. Let's be brutally honest with ourselves, who doesn't wan an OP Mary Sue moment? Now I think part of what helps with that is the First-Person POV we get a lot from Feyre, which is particularly helpful for fantasizing during particular scenes. But the point stands- she is still relatable enough to us that we geuinely feel like she live vicariously through her.
Here's the thing: Feyre's story calls to all of us. It's universal. At some point, all of us have felt lost and we have craved to be found by someone who sees us for who we are. That's what Feyre got, and that's what we all seek. And yeah, this counts a little under the point of living vicariously, but more standalone. Feyre gives us what we want, no matter how absurd the circumstances to get there are.