Normally what I did:
Fired her in the morning and ask her to pack right away. I am the one to wait her in front of her room and make sure she cannot go out to take something not belong to her.
Then drive her direct to the agency. Will call the agent in the car. I will pay her money with airplain ticket fee in front of the agent and ask her and agent to sign. So each parties can have a copy on hand. Need to send the immagration letter to make sure I terminate her and she need to leave in certain date.