THe ball uses the 'Throw item" mechanic of the game, which is usually intended for things like flasks, boxes, rocks, crates, etc. In other words, as an attack. Which explains why your companion feels like you attacked them. Basically the game treats it like you are not passing the ball to them, but that you are trying to attack them with it.
It WOULD be cool if the result of the throw would depend on the hostility/friendliness of the target.
