I would just like to say that your tank is awesome. and... Personally I'd put some pants on and tell her you're getting live plants. But if you really need ammo just make up some stuff. For instance "lives plants will keep our fish healthier because they release enzymes into the water that help gill function"... or "real plants cause less stress on fish because it's like their natural habitat, you want our fish to be happy don't you?. She's not gunna look into that. And if she does then I guess you're sol, and you best hope to christ she doesn't find this thread. lol... But on a more serious note, they really do keep your water cleaner, like MG said. And I honestly do think the fish are happier with them. Mine play in my plants all the time. I go to friends houses and their fish want nothing to do with their plastics.
And I'd get rid of the black lights. Although it might be cool at night, or as an option while you have guests over or something.
G/L to you