vocative comma by default

If I say, "I will go skiing Nonna….." By default are the words preceding Nonna being addressed to Nonna? Or can I argue that my words preceding Nonna are not being addressed to Nonna, but rather, I say the word Nonna to get her attention so that she listens to what I say after her name.

Basically my question is- if we follow a sentence with someone’s name while we are speaking, by default, are all the words preceding a person’s name addressed to this name? Or is this too broad of a conclusion to make? I am asking because my character has Tourette’s and has a habit of saying Nonna after speaking. Can I make the case that by saying Nonna or anyone’s name after making a statement, you are not automatically employing the vocative comma and you are not 100% by default stating that the words preceding Nonna are being addressed to Nonna? How can I make this argument or is this argument even valid?