//Well, this is a complicated answer.  To be honest, I don’t think either of the two would fully realize the feelings they have for one another if it weren’t for something tragic.  They both are this reliable foundation to the other, and even if they did start feeling something more, they wouldn’t acknowledge it for fear of losing that one means of solitude they have in their chaotic world.  According to Sarah’s headcanon, after Jake dies, that’s when Lizzie finally realizes that she wasted so much time being irrevocably in love with her best friend and never crediting it past friendship.  But you also have to take into considering what their setting is—which I think is the main reason why they can’t be happy together.  All 7 years at Hogwarts, Lizzie wanted nothing more to fit in—lying about her blood status; Jake spent his years trying to stand out, being idiotic and always living like there was no tomorrow.  I think in any other universe that would be the deciding factor that completely ties them together; but in the wizarding world during the 70’s, that’s what tears them a part.  I have no idea if I’m making sense, but that’s just my gut reaction to Wolfestein.