In which way does Helen's diction best illustrate her relationship with her sister?

A. through the use of references to shared experiences
B. through the use of words and phrases they made up
C. through the use of condescending and academic words
D. through the use of simplistic and straightforward words
E. through the use of references her sister will not understand

B. through the use of words and phrases they made up

By using words and phrases that they made up together, Helen's diction illustrates a sense of playfulness and intimacy in her relationship with her sister. This suggests a close bond and shared inside jokes between the two sisters.