I would infer that the argument for the cost of the security camera is that she was the only person who was actually caught stealing, and the owner thus believes that she should reimburse the cost of that system. That's not a valid demand, but I can see where the owner is coming from.
The difficulty here is that the salon owner can go to the police, and the tenant stylist is caught on tape, red handed, stealing from her and perhaps also from other stylists. It seems sensible for the stylist to consult a criminal defense lawyer; perhaps the lawyer will be able to negotiate a lower payoff for the stolen products. The stylist is in a poor position to negotiate for herself, and her statements could end up being used against her in court.

