In The Perks of Being a Wallflower, was Charlie's sister sexually abused?

Although there is more than one character in the book who is sexually abused, including Charlie, we never find out that his sister Candace was sexually abused. Charlie was molested by his Aunt Helen as a child, Charlie's friend Sam was kissed by her father's friend at age 7, and Charlie's sister Candace was the victim of dating violence, when her boyfriend "Ponytail Derek" hits her after she gets in a verbal altercation with him,...

Although there is more than one character in the book who is sexually abused, including Charlie, we never find out that his sister Candace was sexually abused. Charlie was molested by his Aunt Helen as a child, Charlie's friend Sam was kissed by her father's friend at age 7, and Charlie's sister Candace was the victim of dating violence, when her boyfriend "Ponytail Derek" hits her after she gets in a verbal altercation with him, on page 11. She tells him that he needs to stand up for himself to his bullies, and after egging him on, he slaps her across the face. Charlie then witnesses them having sex, which occurs on page 12. Later, Derek breaks up with her after she tells him that she is pregnant, but then wants to get back together with her after she tells him it was a "false alarm." Toward the end of the book, after Charlie realizes that he was sexually abused as a child by his aunt, his brother and sister both deny that any abuse occurred when they were children.