Why was my friend Caroline suspicious of Sarah’s motives for friendship with Robbin?

It’s complicated. Basically, Caroline was worried and asked me if my ex best friend (with whom I lost touch, because I’ve outgrown the friendship and she is interested in a guy that’s been chasing me a long time and jealous about it); Sarah; might get obsessed with her brother, Robbin and possessive of him and never leave him alone, because in her words, she seems to want his friend, Benedict; and he hasn’t shown any interest in Sarah. I’m wondering what Robbin has to do with Sarah’s feelings for Benedict; and about Caroline’s motives for asking me if Sarah will get fixated on her brother, Robbin. Is it likely that Benedict and Robbin were worried and asked her to ask me if Sarah is toxic and creepy, is it because the guys in this group generally can’t take no for an answer, or is it the fact that my friend Caroline has mental health issues that have led her to ask me such an odd question? Caroline never liked Sarah, but Sarah has never acted weird or creepy to anyone. Can someone please explain this? I don’t get these people.

Updates
3 mo
No one will give me a clear answer. I tried Asking Caroline about it and she just denied that she’d been asked to ask me.
Why was my friend Caroline suspicious of Sarah’s motives for friendship with Robbin?
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