If Carol thought she is the best in being passive-aggressive, she was mistaken. If she thought she has the monopoly of being childish, she has learnt the hard way. You hate that you are doing this as an adult, but it sounds like a good game the two of you should play. You are equally good in over-reacting.
For three straight nights, you have barely touched whatever she has cooked. True, her cooking has improved remarkably after you unleashed the best beef wet fry last week, but you only touch her food and eat with so much casual disinterest, before leaving it there.