Lots of us say lots of things, when we feel we are not being overheard by the person we are dishing. Often it's not meant as strongly as it might sound. Your mother may feel quite embarrassed that you heard her.

So your relationship with her has fundamentally changed, even though you already knew she was narcissistic and manipulative? What was the basis for the relationship having been as good as it formerly was?

This incident might set the stage for the two of you to have an honest conversation. But no conversation will take place, if you feel this ends any possibility of there being affection between you two. Narcissistic is one adjective. Rarely does one adjective define a person. If your mom has some positive qualities, remind yourself of those before you cut her off. Then you might say somethink like, "I was disappointed to learn what you thought of me, if that is pretty much what you do think of mine.?" She might want to take it back.