With no sign of injury on Zoey, it sounds unlikely that your Boston terrier caused her death by their little tussle over the ball.
An aneurysm is a definite possibility. It can happen with any creature including humans. An aneurysm can just blow out suddenly, and the passing is very quick indeed. Sometimes that is the cause of "dying in sleep", especially when energy the day before has been totally normal, and no signs of any problems.
It is so sad for you though. You must feel so awful and shocked about your little dog, and so must your whole family.
The only possible consolation is that dear Zoey died doing the thing she loved a lot. Chasing the ball....having fun in the snow...with her loved ones -her family. She didn't have to know what it was like to be sick, or old.
But I am very sorry for your loss. My kindest thoughts to you.