The correct answer is that communication is irreversible.
In the given situation, Amber is still hurt due to the things that John had said unto her, especially calling her a "slob". Though they already made up, Amber still feels upset, because she thinks that what John has said is true. John is experiencing the irreversible aspect of communication, wherein communication cannot be taken back, whatever you might have said, will stay that way. It cannot be changed nor taken back.