Senoufou, your Cork mother's usage of 'so' is an Irish way of saying "in that case".
"You won't have any more apple pie, so?" = "Since you're too full to eat any more, you won't have any more apple pie."
"I'll leave it there, so." = "I will have no further discussion about this subject, in that case."
It's used like this: "The plane's delayed an hour? They'll be an hour late, so."