Both green olives (Olea europaea) and Pimentos (Capsicum annuum) contain isoprenoids that are structurally similar to the methylcyclopentane monoterpene nepetalactone, which is responsible for binding to receptors in you cat's vomeronasal organ and consequently the mind-altering effect your cat experiences.
These compounds are not unusual, although thie configuration varies widely between plant species.
These compounds resemble pheromones, and as such some of them function as a natural mock-pheromone pest repellents for the plant, which is likely how such high levels of these constituents within a plants' essential oils evolved.
The vomeronasal organ is what your cat (and most other animals with the exception of humans, although there is a small indented area and partial nerve channel where it would be, left over from our evolution) uses to sense pheromones, and is where the nepetalactone in catnip stimulates pheromone receptors resulting in space-kitty.
Summary - it is likely that either the green olives or pimentos have a chemical in their essential oil that is similar enough to the active chemical in catnip to have a similar effect on the same receptors in the part of kitty's nose that are responsible for catnip getting her high.