I know LuluHB. It was a perfect ending to the book and there's no reason why it wasn't kept true in the movie.

The director of Tomorrow When The War Began is also directing (and screenwriting) the next one and is considering a massive change in there too with one of the characters. I don't understand why they want to change things when the book is a bestseller - it doesn't need to be altered or "improved". Just leave it true to what people know and love.