I dont think Lilly ever saw Severus in a romantic way. He was always friendzoned and then he got himself booted from the friendzone. I do feel sorry for the character cause life **** on him but he just kept hurting himself. Him calling Lilly a Mudblood is really hard to forgive. We the readers can, but put yourself in Lilly's shoes. Its like if you were black and your best friend called you a...well you know. Thats a line and whether its crossed in a fit of rage or not its still a line that youve crossed.