They were friends before they went to Hogwarts. Lily and Snape sat together in the I Never Received My Letter To Hogwarts So I’m Going Hunting With The Winchesters shirt same compartment on the Hogwarts Express. She stood up for him when James and Sirius went at him, as seen in “Snape’s Worst Memory”. And she made excuses for his behavior for YEARS, behavior that included hanging out with wannabe Death Eaters like Mulciber and Avery, and calling Muggle-borns Mubloods.
It wasn’t until their Fifth Year that Lily FINALLY had enough of Snape. And that was only when he used the I Never Received My Letter To Hogwarts So I’m Going Hunting With The Winchesters shirt M-word on her of all people. Voldemort was at Hogwarts long before Lily and James were there. There wouldn’t have even been any years crossing over, so this would have never happened. Magic makes the housework go away, eliminates boring car rides, and helps you make a fool of your school rivals. Start asking questions and it all breaks down. This isn’t hard sci-fi; it’s not supposed to work.
How does magic know how to clean the I Never Received My Letter To Hogwarts So I’m Going Hunting With The Winchesters shirt surface of an object without damaging it? How can magic transport a person without destroying and cloning that person?—this launches you into the same ethics/physics crises that the Star Trek transporter and the Tesla device in The Prestige bring up. Why is it okay to use magic to assault and bully and coerce people? These behaviors would be grim indeed in a book without magic. And why do wizards have no art or culture of their own to study, and yet eschew studying ours?
Why do they learn how to break the I Never Received My Letter To Hogwarts So I’m Going Hunting With The Winchesters shirt laws of the universe without ever learning what those laws are? Why isn’t there a Hogwarts marching band, or shop class, or course in the physical sciences? Either that or there’s a black market on essays, and the same six Ravenclaw students have been composing every assignment for the entire duration of Harry’s attendance at Hogwarts.