Since Sharon was the one who shared this info w/ the OP, I think this info clues us in the Sharon thinks Katie is immature, which would explain why Sharon thought it was her place to "teach Katie some manners" by correcting her about the whole "greet me first before you take my candy that I always put out and always share" thing.
So I'm glad it was there--it explains a lot.
Doesn't make Sharon right. But it explains why she thinks she was. Because, you know, SHE is a grownup, and Katie is flighty and immature.