They said they weren't interested because it's all woke nonsense. It's in the OP.
You are missing the point.
B allegedly said that to the trainer.
OP has only the trainer’s word for that. OP does not state whether the other employees backed up the trainers account. So far, it’s one person’s word you are relying on and you have no idea whether that person is reasonable or not.
I used to deal with complaints for a living, and a complaint is what this is.
At the moment, OP has a complaint from a single person, who gave their point of view.
As a minimum, I would expect her to get B’s point of view. She also has a number of witnesses to the events.
Just as an example, perhaps B felt picked on by A throughout. Perhaps B’s behaviour was a reaction. Perhaps A is lying about B’s behaviour.
On the face of it, B appears to have behaved very badly indeed, but as a minimum, she should be allowed to give her side before any decisions are made about the appropriate action to take. Having done that, you may reasonably conclude that B is every bit as bad as person A said, and act accordingly, but B should always be allowed to respond to accusations made against her.