Reading your comments on A being incorrect, I would have to say C since A is true. Hope this helps :)
I believe the answer to this is Keyword.
Hope I am giving the right answer to the question.
She is engaging in role play which is the act of taking the role of someone else. Since she is pretending to be Cinderella, she is taking the role of Cinderella and imitating the character as a whole. She is roleplaying Cinderella to be short.