Replace confinement nanny

Hi I need help urgently, does anyone have any tips on how to handle if I want to replace current confinement nanny? She actually left my newborn on our high changing table alone and went out of the room! She took almost an hour to feed my newborn and the food she cooked for me caused a lot of bleeding and even diarrhoea. Should I inform agency first and let them inform her? She looks like revengeful kind so I’m worried if she might mistreat baby if she knows I’m replacing her.