Possessive

Ben informed me that he is mad at Lucy. Do I think it's strange that a 31-year-old man is mad at a 3.5-year-old? No, I'm frequently mad at her.

His beef: the other day at Central Market, she was carrying her My Little Pony® doll, and Ben says, "Hey, is that My Little Pony?" And she screams, "NOOO, it's MY little pony. It's not YOUR little pony." He wisely avoided a who's-on-first-type argument with her. Nonetheless, they are in a fight.