Falcon-180B also got it right > Since Sally is a girl, she can be considered as one of the sisters. However, if each of her brothers has 2 sisters, that means

Falcon-180B also got it right > Since Sally is a girl, she can be considered as one of the sisters. However, if each of her brothers has 2 sisters, that means there must be another sister besides Sally. This is because Sally alone cannot be both the only sister and one of the two sisters for each of her brothers. Thus, Sally has 1 more sister.