I'm 99% sure that's her index finger.
You can see three knuckles to the left of her finger.
It looks like she might bo holfing a pen cap or something, and her thumb is bent, pressed against it, so it only looks like her index knuckle, but it's really her thumb.
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 cap or something but if she was flipping someone off i would die!!
