Bella played ball with me yesterday.
It wasn't exactly fetch. Sometimes she brought the ball back. More often she picked it up and played with it by herself - swatting and stomping on it with her feet, pushing it with her nose, tossing it in the air allowing for a second catch, and chasing it again when it rolled down the hill.
But she got excited when I did get hold of it, jumping up and down, and watching and waiting in anticipation of it being thrown again.
She is almost 7 year old and I think she has finally figured out that ball is a great game made better when played by two.
It was delightful.