I’m sick of people saying Snape was the worst friendzone ever. They weren’t friends anymore. He was hanging around death eaters and was dabbling in dark arts. The friendship wasn’t healthy anymore.
That doesn’t make it unhealthy… He was being tortured by her boyfriend and his friends and he couldn’t take it anymore so he found people who liked him the way he was. She dumped him as a friend, not the other way around. He called her mudblood, but it was pretty obvious he attempted to apologize and make up for it. SHE DATED A BULLY OVER A GUY WHO JUST WANTED A FRIEND.
First off, “her boyfriend” is inaccurate: when Lily ended her friendship with Snape, she wasn’t dating James. The friendship ended towards the end of their fifth year (“Snape’s Worst Memory” depicts OWLs), while Lily and James didn’t begin dating until their seventh year (canonically, after James had “deflated his head” and begun maturing.)* Lily wasn’t friends with the Marauders at this point. And, as for “he found people who liked him the way he was” - he was already friends with Lily. And…if the “way he was” includes an interest in the Dark Arts and hexing people, then perhaps Snape needed to actually revise who he was instead of finding people who encouraged that? Lily tries to talk to him about this, but he clearly doesn’t listen (see the moment where he turns off as soon as she agrees about disparaging James.)
Secondly, by their fifth year, the Snape/Lily friendship was toxic and unhealthy. Snape was growing more heavily involved in the Dark Arts and with people who were basically proto-Death Eaters (Rosier, Mulciber, etc.) These are people who are devoted to spewing what is the Wizarding world’s equivalent of racist rhetoric - the people who advocate murder and genocide of Lily and people like her. She dumped him as a friend because he called her Mudblood, but it wasn’t simply because of that - it’s clearly the last straw in a long line of issues Lily has been having with Snape (between Snape condoning what Mulciber did to Mary MacDonald - harmful Dark Magic that Snape dismisses as a prank; Snape calling other Muggle-borns “Mudblood” and using the same rhetoric as his friends; Snape using Dark Magic himself, which Lily abhors.)
Lily’s “I can’t pretend any more” shows that this, and things like this, have been an ongoing issue:
I’ve made excuses for you for years. None of my friends can understand why I even talk to you. You and your precious little Death Eater friends – you see, you don’t even deny it! You don’t even deny that’s what you’re all aiming to be! You can’t wait to join You-Know-Who, can you?
Emphasis there on years. Lily has spent years trying to ignore what she knows about Snape, trying to overlook the things he’s said and done, and this - calling her a slur to her face - is a moment of awakening. It’s the point where Lily simply can’t ignore that Snape has become a person who’s no longer her friend - “You’ve chosen your way; I’ve chosen mine.” That James Potter, who she hates, was willing to defend her while Snape called her a slur and said he didn’t need help from someone like her: it’s not a one-off incident, it’s simply the breaking point.
At that point, apologizing for using the slur isn’t enough, especially when it’s clear that Snape isn’t cognizant of everything else he’s done, or particularly repentant of the other actions he’s done - and his apology isn’t an effort or a promise to change. (Also, Lily doesn’t owe him forgiveness; implying that Lily owes him forgiveness is treading very close to that whole “Lily friendzoned him! Lily was obligated to forgive him! Lily was obligated to fall in love with him!” argument, which is in and of itself complete and utter tripe.)
*whether and how much James improved will hopefully be expanded upon by Pottermore - on one hand, we know that the bullying continued; OTOH, per Sirius, Lily was explicitly not aware of this - cf. the “he didn’t exactly take Snape along with them on dates and hex him,” comments, among others.) And the “Elvendork! It’s unisex!” story shows someone who’s still immature, and James didn’t have a lot of time in which to mature and grow before his death. But then we also have the James who was loyal to his friends, willing to join the Order and fight and who stood up to Voldemort personally three times; who willingly laid down his life for his wife and infant, wandless, in the hopes of buying them a few moments to escape; who, per JKR and per the text, became a better person. But this isn’t about James and Lily, because at the point where Lily ends the friendship between her and Snape, she clearly still loathes James - she’s calling him an “arrogant bullying little toerag” at the same time she’s ending the friendship with Snape. This isn’t about Lily choosing James over Snape - it’s about Lily choosing to walk away from Snape. James wasn’t in the picture.
And Lily had every right to end that friendship. Lily didn’t choose “a bully over a guy who just wanted a friend” - she chose someone who actually respected her over someone who called her the equivalent of a racial slur and who joined an organization devoted to the murder of people like her. Look at their later actions: James loved Lily and gave his life trying to give her a chance to escape. Snape, despite professing love for Lily, would have been willing to let Lily’s child die if it meant that she could be saved. Is that considerate of Lily’s feelings or Lily herself? No - that’s treating Lily like an object - it’s obsession, not love.
(And, actually, at this point in fifth year, Lily doesn’t choose either of them - she chooses to walk away from an unhealthy friendship with Snape, and she chooses to ignore James until she sees that he’s changed. So there’s that. And…to suggest that Lily had to pick Snape or that she should have chosen him…no. Snape didn’t respect her. Snape became a full-fledged Death Eater who believed in the cause after graduation. Snape didn’t care about what Lily wanted - he cared about wanting Lily. (“You do not care, then, about the deaths of her husband and child? They can die, as long as you have what you want?” The answer to that is an obvious, emphatic yes - Snape would have been totally fine with letting Harry die had he been able to secure Lily’s safety. Dumbledore’s “You disgust me” is there for a reason.)
Also, the entire term “friendzone” is complete and utter bullshit, implying that Lily owed Snape romantic love and sex because he befriended her, but that could be another post entirely. (Nobody owes anyone else romantic love/sex because of friendship, people are not some magic vending machine you put friendship coins into until sex comes out, and Lily’s friendship is not some crappy second-place prize. Lily is not a prize. People are not prizes. That is all.)