It appears to be a passive-aggressive power struggle. You didn’t say if chocolate cupcakes were her favorite and she wasn’t going to fix two different kinds. It may also have been a game that they used to play with other people’s minds.
If my wife wanted blueberry cupcakes, I would fix them with fresh blueberries. Instead, I fixed her a cheddar cheese omelet and myself a hot cereal with raisins this morning. She fixes lunch.