Lorenzo's sister

From the book, we know that Lorenzo's sister is 23 years old. She was a very beautiful girl two years ago. However, now she become too skiny, sick and homeless. I think she is a very sel-important girl. We can see from she reject the help from her father. She has a really bad relationship with her father. Also she is a really smart girl. She use the weakness of Lorenzo and let her get into the cellar.