I'd heard a lot of people reference this story and I'm really glad that I found it, your overall execution and characterization is flawless and you have a lovely way with description, particularly when setting the mood for a scene. I particularly loved this exchange:

“Lavender Brown’s got a detention?” Ginny said in disbelief. She was sitting in an old armchair in the Gryffindor common room attempting to correct a Charms essay. “What did she do? Not crawl convincingly enough to dearest Alecto?”

“Leave it, Ginny,” muttered Neville. “I told you before; we can’t start fighting amongst ourselves.”
It does a great job of showing the stress that everyone's under in the new regime and the way it's making friendships start to crack. Acknowledging the in-fighting and arguments even between friends that would realistically take place in so stressful a situation, when everyone's being asked to decide who to trust, makes Lavender's eventual decision to rejoin the D.A., and their willingness to accept her back again, all the more powerful and moving.

I haven't seen many stories about Blaise, but after reading this he seems like the perfect character to put in this situation. You weave your own original story in with the canon flawlessly--we know that Blaise has always been an outsider, and that Snape would be anxious to find a Head Boy who could help subtly protect the students without raising the Carrow's suspicions--it would seem that a "reluctant Slytherin" like Blaise would be the obvious choice, and I appreciate the fact that this story acknowledges that not everyone in the house has to be completely evil and consumed with pure-blood mania. Blaise's reasons for staying under the radar make sense due to the difficult position he's been placed in, and just like with Lavender's no-win situation you do a really nice job getting the reader to appreciate Blaise's predicament, and even view him from a different perspective with lines like:
“You’re a Gryffindor, Lavender, and you hate Slytherins,” Blaise replied starkly.

“That’s not true,” Lavender began, but then she stopped. It was true. It had always been true. In six years of school, she’d never thought Slytherins could be anything but bad. She sighed. “You may be right.”
The "outsider" view that Blaise can offer is interesting to read, like when he explains to Lavender how the Carrow's would view her run-in with Crabbe; I like that you've taken advantage of the fact that you're using a character who would have "insider" knowledge of how the enemy thinks to reveal a side of the situation that a Gryffindor wouldn't normally see.

As others have mentioned, I particularly liked your characterization of Ginny in this piece. I feel like some authors have a tendency to want to display the more major canon characters in the best possible light, but you neatly avoid falling into that trap here by showing an honest rather than perfect depiction of Ginny that seems appropriate to what we know of her character. I particularly like Lavender's line "Why should I change when you have such a high opinion of me?", because it reflects both the characters so well. Ginny's surrounded by family members who have all decided to fight, so I think she would be one to see the decision as more black and white, and have trouble empathizing with those caught in the middle. Lavender's position seems like the one that would be the more common among most students, however, so I'm really glad that you chose to tell the story of someone who is a bit more unsure of where their loyalty should lie. Combined with the inclusion of Lavender's promise to her father, the choice she has to make seems particularly realistic and difficult, and as a reader I really feel for her and the impossible predicament that she's been placed in.

Author's Response: Thank you very much for the well thought out review - it really is appreciated. I've long been fascinated by what happened in that final year at Hogwarts without the Trio, there must be a lot of stories there. Lavender has always been a character who he's oft maligned simply because she was a bit gushy over a boy (and Ron wasn't exactly blameless) so I wanted to give her a bit more of a back story and show her growing up.

As far as Blaise goes, once I realised that he wasn't in the least impressed with Draco (HBP) and was also not mentioned as being in Umbridge's Inquisitorial squad, then I didn;t see why I shouldn;t have a bit of leeway with his character. I get annoyed when all Slytherins are portrayed as evil, plus JK did say that some Slyths returned to fight at the battle, so why shouldn't Blaise be a good guy. He's still selfish, but deep down he knows what's right.

Anyway, thanks again and I hope you enjoy the rest of the story ~Carole~