Hello hvert,
Thanks for your advice. I do appreciate it as well.
We used to have this mutual friend. But she wasn't really nice to the both of us(me and my friend who I am worried about). After this mutual friend left to join a popular group of girls (there were initially 3 of us here), the friendship between the two of us(me and that friend who I am worried about) was stronger than before.
Unfortunately, other than this mutual friend we both know, I don't know any other friends who know this friend who I am really worried about.

But, thanks, hvert, I learn something new and what you said helped me to ease my worry. Thank you so much.
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~~~Stay Strong And Keep Fighting~~~