Is there a room in her house, maybe the kitchen or a spare bedroom, where she could let him run loose even when she's not around? If there's a door she could shut to keep him in one room, and just bunny-proof that room by covering or removing any electric cords, that might be preferable than Happy just staying in a cage most of the time. Whatever room she chooses, of course his cage and litterbox should be there, and maybe an empty cardboard box for him to chew on/hide in, and some bunny toys, that would probably keep him happier.