Answer:
She was feeling state fright. It is natural. She froze up as a natural reaction to the fear of messing up. Since she is in front of "at least a hundred people" she was worried shew as going to make a fool of herself and mess up. She was also more nervous because she was wearing a new dress and something she wasnt used to wearing. All of these made her more terrified because she wanted to succeed and to do well on the piano.
Step-by-step explanation:
She was probably feeling nervous.
Evidence - Cara tried not to fidget in her new dress. There were at least a hundred people in the audience, what if she messed up?
I don't know if this really works but here you go!
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