Sanji has mixed feelings about his sister. He cares about her to some extent because she’s the only one who ever loved him and she saved his life, but she didn’t do anything to protect him from his brothers during his childhood. She let him suffer and went as far as making fun of Sanji along with her brothers because she was afraid of getting bullied like him. For a long time, her own well-being was more important to her than Sanji’s.