Answer:
According to the passage, the central conflict that occurred which had to do with Millicent and her confusion about joining the sorority led her to realize that she valued her freedom of movement, association,etc.
It also made her to realize that she wasn't really into the sorority because of her sense of individuality and the priceless friendship she had with Tracy which she could not sabotage for anything including the sorority.
She changes her mind about the Heather Birds and revolts, making the decision to speak her mind.