It is Penn Foster's library.
The first involves the purchase of a new dress, and the second involves borrowing the jewelry she feels is needed to accompany it. It is only after she has borrowed the diamond necklace from Madame Forestier that she feels she can make a suitable appearance at the ball.
C towards that understanding
Answer: an invasion of a castle.
Explanation: "They enter my castle wall!"
I hope this helps :)