McGonagall doles out detentions. Lily can take any punishment as long as it distracts her from her unruly feelings for a certain sixth-year rule-breaker. Kinda-sorta in the "Month of Sundays" universe, but feel free to imagine otherwise. (Mostly) fluffy one-shot.
Immediately following Deathly Hallows, before the Epilogue. Harry thinks on his struggles and victory and spends some time with Ginny.
Severus watches Lily fall for James. Epilogue to "A Month of Sundays" /s/5249018/1/A-Month-of-Sundays
How does Lily discover her buried feelings for James Potter? Picks up from James's and Lily's 5th year, shortly after Lily ends her friendship with Snape.