Source: The Great Interpretation of Dreams (Ibn Sirin)
A sister in a dream indicates sharing in goodness and sustenance. Seeing her indicates joy, happiness, and the arrival of an absent person.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
A sister indicates intimacy and love. Her death indicates the death of an enemy or weakness.
Source: Signs in the Science of Expressions (Ibn Shaheen)
A sister is interpreted as goodness and benefit. Whoever sees her will attain goodness.