I have a 13 month old boxer female called Roxy. I walk her every day at my local field with a friend who has a female border collie called Ria. Roxy is very possesive of Ria and will not let her play with other dogs or go near them. Roxy will bark and fight with the Ria and run in between her and any dog that goes near her. Roxy will also constantly bark and try to play with my Ria which makes her look a thug. Ria is so not interested in playing but as of yet has failled to tell Roxy this. Has any one any ideas how to deal with this as it is beginning to ruin our daily walks. This has been going on for about four months now.