I'm a little confused by this.
You've decided that your friend is waging a vendetta against your seven year old son, based on what? The fact that your other friends assured you that she'd made an allegation that your son pushed her daughter off her scooter, hoping that she would die??
It sounds really implausible, I'm afraid. Have you heard this allegation from the horse's mouth, i.e. directly from your friend? All I could pick up from your posts was that she'd said that she'd been meaning to talk to you about his behaviour for some time.
Is it so inconceivable that your son is badly behaved at times? It strikes me that your friend may have genuine cause for complaint but that your friends have worked it up into "she thinks your son is a devil child!" and you've obediently started fizzing with indignation, calling a halt to the friendship with no further discussion etc.
How do you know what she "genuinely believes"? How have you, and others, decided that she's a "queen bitch" and a psychopath?
There's much more to this than whether you hand over a present. Why don't you actually listen to your friend and talk to her one to one? The other friends probably feel bad for stirring, and that's why they want you to reconcile. It's also why they don't want to discuss it any further.
Incidentally, I don't say that this applies to you, but in my experience, people who grouse about members of their social group being "manipulative", "outwardly charming" and "knows everything" feel frustrated because the person in question is cleverer than them and has won a logical argument with them.
I'm a bit confused by the bit about your colleagues, too. What has that, and your suspicion that one of them reported you for crying in the ladies, to do with the situation with your friends?