My little Luna is a jealous one. She was here first, and a couple of months later we got Izzy. Lucky for Luna, Izzy is VERY laid back, or she'd be in big trouble because she's half Izzy's size
When Luna is acting like queen bee, she gets put back on the floor and ignored for a while and that seems to stop the jealousy for a while. She needs to be reminded once in a while that she's not an only child