I talked to her in the morning after sending my kids to relatives' house. It is preferable that you have a third party, such as your husband or a relative on the site to protect you.
Although she did wrong and you fire her, I think she could seek assistance easily (such as to find boarding house) iin the daytime. May be this can help you.
Last year, I fired my bun bun in the following procedure :
1. Prepare the termination letter, stating the fact why you want to terminate her with examples. Make sure she signs on it before she go.
2. Prepare the one-way ticket (valid for one month as advised by my friend who was working in Labour Dept though the regulation only mentioned 2 weeks)
3. Prepare the compensation, hard copy with all the detailed calculation for her to sign receipt and of course cash also (wages and the notice of payment, annual leave balance, etc)
4. Ask my hushand to bring BB to the playground, don't let BB stay at home.
5. Ask my friend (better a male and third party, if no, ask the security guard of your building) who is a policeman to witness the whole process. In case any disputes, he can help.
6. Present the termination letter and the compensation details in the morning and make sure she could leave before noon, explain to her your reasons of termination in a generous tone. If she disagrees, don't argue, emotional communication may create the excuse to Labour Dept. Just insist your decision, no more discussion, just calm and generous to her. If she still insist and reluctant to leave, call the police.
7. Ask her to pack all her things in one hour time and leave.
8. Of course, before she leaves, she has to return all the property you gave her ie resident card, keys, etc.
9. Change the lock of the house, inform the management office that she has been terminated and ensure no enter into the building again.
10. At last, inform the Immigration Dept, etc.... the normal procedures.