If you breed a male of the same species with the female, there's a 50% chance the male's ball will be passed down instead.
So female Ultra Ball vulpix with male Luxury Ball ninetales; half the offspring have an Ultra and half the offspring have a Luxury.
I suppose (since I only have a Ditto and not a second Vulpix) I would have to trade for another Vulpix in a Ball I like, then?