The first week Charlie was with us, he was polite with Cricket but would not play with her. She wanted to play so bad and would drop a toy by him but he would just ignored it. (He would chase a toy if we threw it and bring it back.) As the week progressed he would lay near Cricket and watch her chase balls. I would throw them both toys and they would chase after them together. Well, the last couple of days he has played tug of war with toys with Cricket, soo cute. She must sense he is much smaller and is gentle with him but of course never letting him win the toy.
I feed both the dogs at the same time in the same room. We have never had any food aggression from him. I also give them treats together. A couple of times when I have been laying on the couch and Charlie has been laying next to me, he has let out a soft growl when Cricket jumped up also. Nothing more than that, Cricket found her place with us and all was well. I'm not sure if he didn't wanted to share his human or was just afraid of a big dog jumping up his way.
He still prefers people but I am happy to see he is interacting more and more with with my dog, Cricket.