Is that what gave me away? Aaah, maybe I should have gone out there with them, but I can keep an eye on both of them from over here.

[If she was out there handing things out then she might lose track of one of them. No way does she want to lose one of her Dittos here.]

If they could remember to say 'hello' and some other phrases then they would be even more convincing. Just as well you were going on appearances and nothing else, otherwise it would have been even more obvious which one was the real me.