Renee! I read the first five chapters of this ages ago and I could have sworn I'd reviewed this before, but it look like I didn't! I'm so sorry. I am the worst. So I'm going to make up for that now!
First here is me gushing about the story as a whole. I love this. Your portrayal of Petunia and Lily is so adorable, so touching, and so realistic. Petunia as a child is not always nice, but I can really understand her. Maybe because I'm an older sibling myself, but all the moments when Petunia is jealous of Lily being so doted on and the golden child of the family - I could relate to Petunia. And what I especially love about the way you write their relationship - of course they fight, and they're jealous of one another sometimes and try to look cool in front of their friends and don't always get along, but at the end of the day, they are sisters and they care about each other. I loved the chapter where they're on their pretend boat, it was adorable. I just love the realism of the way you portray these two characters, and the sweet sisterly moments between them are even more special knowing how it all turns out later.
Which makes this chapter so much sadder. It felt like a long string of misunderstandings, and reading this chapter I just felt like it didn't have to be the way it was! Even after all that's happened, Lily is excited to tell Petunia her thoughts about Hogwarts and says she'll miss her sister, and Petunia backs Lily up in that scene when Lily's parents find out about magic. Until the last section of the chapter, it didn't feel like she thought Lily was a freak, just that she was sad to be left out of all the excitement, and annoyed that Lily could share that excitement instead with Snape, whom Petunia hates.
And then they fight, just as Lily's about to leave for months, which means they leave on a bad note, and then you have that ominous ending line about a storm coming. You've had all sorts of symbolism in the story so far that I really love - they used to sit through the storms together, and Petunia was afraid of storms (which is so appropriate, because here you have storms symbolizing conflict, and Petunia totally demonstrates this aversion to conflicts several times - not thinking about Snape's background, covering for Lily at the slumber party... it's all there and I can tell how much thought you put into it - it's fantastic. Anyway, before I got sidetracked talking about your excellent symbolism, I wanted to point out that the end of this chapter made me sad, because it really feels like the point where they stop being friends :(
on the topic of less sad things:
She’d been on the phone arguing with Susie, and his lecture interrupted her phone call. It was totally embarrassing. -- haha this is classic! Daaad, stop embarrassing me in front of my frieeends! this line made me laugh.
And I loved the appearance of McGonagall arriving to explain about magic. Everything about that scene was wonderful :D
this was such a great chapter, a wonderful story overall, and of course that a/n about you having a backlog of finished chapters makes me very happy as well.
now go summarize your research article. :P