Because I know my Sugar Wolf so well, I can tell that this photo was taken while one of my three cats, Leo, was slinking around, teasing her, and trying to get into our space. Leo is my Mr. Big, so Ruby has an unmanageable jealous streak about him.
Leo is really asking for it here. Because Ron is the Alpha Male, when Ruby wraps her jaws lightly around Leo's tail, or snugly around his neck for that matter, it's only to get his attention. It's not to hurt him. Only the Alpha Male can do that. I just made that up.
And no matter how important it is to keep her eyes on him and not let him into our space or near me, this would be the look I get when I ask her "Do you want to go for a ride".