You could try the Feliway/Safe Space infuser. It's a plug-in diffuser that you attach a little bottle of a smell-alike for the Eau de Kittycat that cats' facial glands produces. It basically means "this is a safe place, all's well, you belong here." Humans mostly can't smell it (I have a hypersensitive sense of smell, and to me it only occasionally smells very lightly of coconut and cedar) and it's really easy to find. Just getting to spend time with you will probably help too.