Basically at a friend's house and they were dog sitting a neighbours collie. My dog is a bouncy cockerpoo both are females. My friend has a male cockerpoo so out dogs play lovely together. They did sniff and play a bit of attention to each other but were not overly amused. But then the collie wanted to play a game of fetch so my cockerpoo tried to join in the collie pinned my cockerpoo by the neck against the floor and made her cry! It seemed quite aggressive and yet she seemed a lovely dog. I am just trying to work out if it's a female thing or breed thing. My dog gets jealous and barks but she is never, ever aggressive.