Don't let her know you prepare to fire her.
When you fire her on that day, just pay One Month Salary (唔慳得) , prepare all the expense (Air ticket, annual leave, travel allowance ....) and call the agent to help her to collect her luggage as a Witness. Send her back to Agent. Remember check she already signed each payment every month and all the related payment receive.
Protect yourself. 賓賓 have many assoication to teach them how to prosecute you unreasonably.