Being negative is an insult. "You're fat"

"Neg" is a joke in a light hearted way a bit cheeky. But really if you put to much into thinking about it, they just come off as an insult and you don't need them anyway. If they come out in natural conversation great if not who cares.

I'd much prefer to use the "breaking report" mentality i.e. just have a cool conversation but if she does or says something you don't like you basically show you don't stand for that shit and can quite easily walk away. Same effect less likely to go wrong then deliberately trying to put in a preplanned "neg"