There could be various reasons why a girl might perceive that her best friend isn't nice to her anymore. Here are some possible explanations:
Change in Behavior: If the best friend's behavior has changed noticeably, such as becoming distant, less attentive, or showing less interest in spending time together, the girl may interpret it as a sign that her friend isn't as nice as before.
Communication Breakdown: Lack of open and honest communication can lead to misunderstandings and assumptions. If there has been a breakdown in communication between the two friends, the girl might misinterpret her best friend's actions or intentions.
Shift in Priorities: People go through various life changes, and their priorities might shift over time. If the best friend is preoccupied with other commitments or new relationships, the girl may feel neglected or less important in her friend's life.
Conflict or Disagreements: Arguments or disagreements between friends can create tension and affect the perception of niceness. If there has been a conflict that hasn't been resolved, it may contribute to the girl's belief that her best friend isn't being nice.
Insecurity or Low Self-Esteem: Sometimes, personal insecurities or low self-esteem can influence how someone interprets others' actions. The girl might perceive her friend's actions negatively due to her own feelings of inadequacy.
Comparison to Others: If the best friend starts spending more time with other people or seems closer to someone else, the girl might feel left out or replaced, leading her to believe her friend isn't being as nice as before.
External Stressors: External factors like stress, personal challenges, or changes in their lives might affect the best friend's behavior unintentionally, making the girl feel like her friend isn't being as nice.
Feeling Unappreciated: The girl may feel that her efforts to maintain the friendship aren't being reciprocated, leading her to question her best friend's niceness.
It's important to remember that perceptions can be subjective and influenced by various factors. If the girl is feeling this way, it's crucial for her to communicate openly and honestly with her best friend to understand the situation better. Honest conversations can help address any misunderstandings, resolve conflicts, and strengthen their friendship.