I'm sure that Lily knew quite a bit about how Snape was treated, and that her sister would have been as mean as this story makes her out to be. Lily would have sheltered him, and I think her parents would have understood if they'd discovered him. But Petunia, no.
Author's Response: Yeah, I really like the friendship between Snape and Lily that was established in Deathly Hollows, I just want more of it. I agree, that Lily's parents appear to be sympathetic and kind in the books. Petunia is the odd person out in her family. In a way I think she in Snape have a unpleasant understanding of one another and are a little too similar in some ways. Thanks for continually reading and commenting on my stories. Cheers!