My 15 month staff x bitch is ball obsessed. This has been a great recall training aid as she is totally focussed. However, recently she has been agressive to other dogs if they so much as sniff her ball. She has now had a few nasty fights with other dogs over her own or their ball. Without the ball she is also back to her bad habits of not returning when called and jumping up...

Please somebody help me, she is a very submissive and friendly dog any other time but has become like Jeckyl and Hyde.