This situation is no different from having a teenager and a toddler. The teenager (
Luna) has totally different interests than the toddler (Spike). To
Luna, Spike
is interesting and amusing for a couple of minutes and then he becomes annoying, To Spike, everything is always interesting and amusing and and he will want more attention from Luna than she is willing to give. She is telling him, enough, leave me alone now. It is more communication than dislike or aggression.