Inverse Logic...guilty or innocent?

Yesterday, as I was chauffeuring the girls around to our appointments, lo and behold...we were a little early! Knowing that Tressie has low blood sugar and that we wouldn't be home before she "crashed," I bought the girls an M&M blizzard to share with one another. SO I passed it to Macy along with a spoon and napkins, and I asked them each to carefully take two bites and pass it on to the next! Simple enough...right? Well, after a minute or two, I overheard Annie excitedly shout, "Hey! Now let's do it in the inverse!" Shocked that she knew that word and actually used it correctly, I continued driving thinking of how proud I was of them...my sweet girls using intelligent words! Then after a few more minutes...and they were still passing it back and forth, it came to me... Annie was sitting in the middle of the passing line! So if they were to share with Macy passing it on to Annie, then Annie passing it on to Tressie, then the inverse! Annie was getting double dibs!!! That weasel! I tried not to laugh; I tried not to accuse (since I can't be absolutely sure that she wasn't innocent...can I?); I tried not to fuss at Macy for not catching Annie in this ice cream heist; and I tried to be the responsible mother and to explain the math and logic of passing it: Macy, Annie, Tressie, Annie, Macy, Annie, Tressie, ...! No one seemed to be following my logic, so thankfully I heard a slurp and the whole thing was tossed out the window...conversation, cup and all! (At an appropriate receptacle!)