Final answer:
The client's statement that represents the defense mechanism of reaction formation is the one where she expresses exceedingly positive feelings towards her mother despite previously stating the opposite.
Step-by-step explanation:
The defense mechanism of reaction formation is where an individual expresses thoughts, feelings, and behaviors that are the opposite of their actual inclinations. Using the information provided, the client statement that represents this defense mechanism is C) "I have a very wonderful mother whom I love very much." Although the client previously expressed hatred towards her mother, this statement shows the client conveying a very positive feeling which is the opposite of her true feelings, fitting the definition of reaction formation.