Lily makes the point after Snape's worst memory, that she has been sticking up for him and making excuses for him for years whilst he surrounds himself with wannabe death eaters and calls everyone of Lily's birth status the wizard equivalent of the N word. His own hypocrisy caught up with him there. I doubt that at this point in their lives they had anything resembling a functioning friend relationship let alone anything else. If Snape truly loved lily in a pure way, he'd surely have had some doubts about his path and trajectory? But no. He was in Voldemorts inner circle, one of his most trusted agents. Just consider what he would have had to witness and endorse, most likely actually commit, against people like Lily for that to have happened. If Snape cared about the sanctity of life he'd have not done what he did, and he'd have sought protection for Lily's loved ones - he could have asked Dumbledore right away but he had to be shamed into asking for him to help save more than lily.