Let's sign a BFF contract like this please.

I feel that if that person is really your friend, you should defend her no matter what others say about her.
'The trust is gone the moment you doubt me.'
If you can believe others so easily and leave her, are you even considered yourself a friend to her?

You should study cognitive, it teaches you that everything a person said might not be reliable unless
that person have CREDIBILITY or EVIDENCES.
Perhaps, that particular person have vested interest or hidden agenda?

'Believe nothing of what you hear, and only half of what you see.'

地球在转, 人在变, 你去吃大便