First I want to say that I'm no expert and I'm just telling you what we experienced, so please take my comments with a grain of salt. When we got Dakota 2 years ago our older girl was 12 yo. Dakota would try and play with her and Marti would growl and nip at her. We never left them alone together and monitored them very closely. Dakota wouldn't give up and each day would try and play with Marti. After a couple of weeks Marti started playing back. They would play a lot. You could tell when Marti was tired of playing because she would give Dakota that serious bark and nip at her, not actually touching her. We commented that she brought a little life back into Marti. Fast forward to now. Marti doesn't play nearly as much and Dakota now plays with our new girl Jackie. Dakota is a very sweet girl and doesn't show aggression towards anyone. Well, unless you count the guy trying to sell something at the door a few months ago. She just did not like that guy at all, lol!