It means your two statements do not logically follow from one another, typically to be point of absurdity.
In this case, you saying Nika forgot to mention you is followed by you sayi g Nika scum slipped, Gramma is saying those two things do not follow from one another logically (because you haven't established the scum slip).
In this case, you saying Nika forgot to mention you is followed by you sayi g Nika scum slipped, Gramma is saying those two things do not follow from one another logically (because you haven't established the scum slip).
Pretty simple logic