Question: Why is Ma beheading a rubber chicken after dinner, even though she's tired from a ride with 7500 feet of climbing, including a substantial dirt section, earlier in the day?
Answer: Nimue is going to be a prairie girl who is making chicken for dinner for Halloween. Costume required for school parade and Fall Festival today. The cardboard cleaver, still to be made, is not needed for school event, since fake weapons are banned. We're sort of skimming the edge of the "No blood" rule (with her teacher's blessing).
Note: The decapitated chicken has been carefully engineered with magnets so the head can be detached and reattached.
There's an excellent demented juxtaposition of the cute and the macabre that seems to come in at this age.