Chase me

Going to the park I throw a ball for Ellie. Ellie goes after the ball with Sophie hot on her heels. When she catches Ellie they run back with Sophie holding on to Ellie's ears.
Now when I want a rest I give the ball to Sophie and a new game begins. This morning she held on to the ball for 10 mins playing "chase me". When Sophie lies down for moment Ellie looks to me "get it off her mum". Ellie won't grab it off Sophie and only gets the ball if it is dropped. Sophie loves this game when running she will look back even cross Ellie's path to show the ball.