Great writing. Killing Cassie's mother before she was even born would be indeed great catalyst for Cassie's developement and exelent action twist. You really did improve the story.
Or maybe she was born before war instead? It would make her at last few years older than miss Briggs - remmember that her revenant father was about to kill Sonya. Sonya during her early parenthood surely wouldnt be able to take part at war, it also takes another 9 months to ms Briggs to be born. Realisticaly, Jaqui would be younger than Cassie, at last 4-5 years younger.
In the end, you are exelent reminder, why fanfics suck ass in most cases.