Regardless of where you stand on Snape or Lily's characters/choices, or their relationship, Lily didn't friendzone Snape. He never told her how he felt, so technically she couldn't reject his feelings. It's debatable what would've happened if he had, but here's a quote from an interview in 2007 w/ J.K. Rowling:
Interviewer: Did Lily ever have feelings back for Snape?
JKR: Yes. She might even have grown to love him romantically (she certainly loved him as a friend) if he had not loved Dark Magic so much, and been drawn to such loathsome people and acts.