We had the same situation with our Doxy female, now 1 yr, 1 mo old. We have had her since she was only six weeks old, raising her with our (adult) cat. And, it went through the same exact behavior as what you have described here, and I found it rather amusing. Eventually, our Doxy ("Gretta") became increasingly aggressive with the cat, yet I continued to let her play with the cat, thinking that it is good exercise for her. HOWEVER, just a few weeks ago, the cat "nailed" Gretta with her very sharp claw right behind her nose, almost near her eye; and her claw was "stuck" in her nose with Gretta crying vehemently to be released. I had to physically remove the cat's claw. Not a very good sight to see. Since that time, I'm no longer letter her "play" with the cat, as all it would take is ONE time to catch Gretta in the eye. I love Gretta FAR TOO MUCH to take the risk of letting that happen and for her having only one eye for the rest of her life. It's best to keep dogs away from cats for this reason - period. Just my thoughts.