Yes, cats can get depressed.
She will probably feel better when dh is back.
Keep an eye on her food, if cats go too long without eating, they can develop fatty liver disease, which is deadly. But that probably won't happen if she is only feeling bad for too days.
Does she normally eat only dog food, or is she only doing that now because she is depressed? Dog food does not provide enough protein for cats. Cats have a higher protein requirement than dogs.