Pointbreak
Dude, you should take a break or try to sketch out a new arc, because, if you are starting to forget your characters, you are starting to lose interest in the story....And as a side-note, the best way to make it seem like you didn't forget about her was simply resoning that they left her home to sleep(it was night, she had no reason to wake up). they did after all, go to a presumed warzone, why take a child with them.
the novel does indeed have a lot of minor plot holes. this however, is not one of them. Mia, as of now is a minor character that the Green's just came in contact with. So it's only natural that they forgot about her when she was out of sight. it would have been stranger if they had insist to take along the sleeping girl to a battlefield in the first place. Besides, leaving her there can possibly branch into other plot devices.