@Mackaysgal92 I haven't finished the current chapters yet, so maybe you've already done it, but I think that Emmy should have some sort of goal that isn't just staying with Will and them keeping each other safe. I know that she sort of wants to go home but I feel that she also should have some sort of immediate goal or objective that relates to the war, although I'm not sure what that could be. But as I said I haven't finished reading the current chapters yet, but I am loving the book♥ This is only my opinion and I don't want to offend you in any way. I hope that you understand how much I am enjoying this amazing book and keep writing it!
I also don't think that she's to "Mary Sue" because in the chapter I just read and in past chapters, she has lashed out and gotten angry at other characters, she has broke down crying( like any person who suddenly found themselves in a war zone would do) and can't do things like swim. You've done a brilliant job of making her strong but still having realistic flaws, which makes her a great OC.