1. Jealousy or competitive psychology: My sister feels that her younger sister is getting more attention or affection, which leads to jealousy or competitive psychology, and feels that her position or resources are threatened, so she adopts crowding-out behavior to safeguard her rights and interests.

2. Changes in the growth stage: In the sibling relationship, the age difference leads to the elder sister's need for independence and desire for autonomy in the process of growing up, hoping to gain more freedom and space, but showing rejection or alienation to her younger sister.

3. Influence of family environment: Family dynamics, parent-child relationship and family education methods will also affect the attitude of sisters towards their younger sisters. Parents' partiality, unfair treatment or role expectation will all lead to tension between sisters.