Do not wait until she shows up Monday, because you know she will, to address this. Email her a copy of the termination letter and state that any further contact is unnecessary and any more attempts on her part to contact you will be considered harassment and you will take legal action if necessary.

Any normal person would have realized after the third phone call that was not returned that it was pointless to continue calling and stopped. Any phone calls after three shows her level of craziness and you do not want that at your doorstep.