Is Mackenzie Foy giving the finger at Comic Con?

I don't think so. I think it's just her index finger.

I'm 99% sure that's her index finger.
あなた can see three knuckles to the left of her finger.

It looks like she might bo holfing a pen キャップ または something, and her thumb is bent, pressed against it, so it only looks like her index knuckle, but it's really her thumb.

No. Thats her pointing finger.

yes that is her index finger Mackenzie is to sweet amd kind and young to be doing that and plus there is three fingers to the left of her hand she is probally holdinga pen キャップ または something but if she was flipping someone off i would die!!