What is the solution to losing self-confidence and destructive jealousy caused by the fiancé's sister, especially given the necessity of dealing with and living with her, after the fiancé stated that his sister is more beautiful in appearance and dress?

The questioner made a mistake when she asked her fiancé to compare her with his sister, and this led her to feel a loss of confidence and jealousy. The fiancé also made a mistake by being forthright with her. She must be patient and seek reward from Allah, and work to overcome her situation by turning to Allah and supplicating, with certainty that the entire matter is in Allah's hands. She must also improve her self-image and boost her self-confidence, stop making comparisons, not surrender to negative thoughts, define her life goals, and not be jealous of her fiancé's sister; rather, she should help him maintain ties of kinship with her.