So sad, and so bad, and far too much of this kind of treatment being meted out to workers. Scratch the surface, and you will probably find 'Bella' is a relation or bed-pal of someone further up the food chain - hence acts like a bovine and is tolerated. She was probably jealous of the good standing of 'Jessie', and so made her the target of her fond attentions.
Yes, she should go to the CAB and to ACAS, and should seek support for the process of getting compensation from these pathetic barstewards. I'd suggest in the circumstances that seeking to get this job back is a bad idea - they will get at her again, they always do. But having an employee arreted and demanding an apology for something they cannot demonstrate that she did is unacceptable. It might be worthwhile also consulting a no-win, no-fee employment law specialist.
Re. tribunals: large organanisations with extensive HR departments will fight these and use bery dirty tactics. Smaller firms can try to do this but don't have the resources or the cojones, so if the experts supporting Jessie suggest this route it might serve her purpose.
Good luck to Jessie, help her to be strong and pull through this terrible time. God rot the vile bullies of this world.