I definitely agree... just, dont allow them to play with toys/eat rawhides/eat meals together without supervision to prevent anything bad, if you think he was really being aggressive. Dogs growl, bark and snap all the time! Thats how they teach hyperactive puppies boundaries, and Lucy is probably trying to push Kodie right now. If she is trying to steal his toys and he reprimands her, that is totally fine, as long as he knows to stop and not to hurt her. If you're very worried, just make sure some one is always watching when they have toys in the same room together, to stop a fight if Kodie is too rough. He probably was only telling her to leave him alone

Also, make sure Lucy *knows* that Kodie is alpha by feeding Kodie first, giving him treats first, petting him first, and giving him more privileges. She will get the message, and that'll help put them in their positions