To be angry?

I moved house and had to give notice on my nanny of 4 years with only a few weeks left before new school year. She said it would be extra expenses and time and she could no longer work for me if they were not being paid.

Now I find out that she saw my son in a playground. She had told him that the reason she couldn't look after him anymore was because I was not paying her for the extra time and travel and not just because she couldn't do it. I am very angry. What should I say to her? I am also angry that my ex reinforced that message and explained to our child the same thing nanny had said. (He was also at the playground with my son.)