When the neighbor comes to borrow a cup of sugar, I'm going to give her salt.
That's a little petty. Why give her salt when she asks for sugar?
I want to be mean to her.
You should share with her if she asks. You shouldn't try to trick others like that If they ask for help.
It's called a joke, I know she will figure it out.
Even if it's a joke, I don't think she would think so once she uses it. How do you think she would feel when she gets overwhelmed with saltiness and begin to distrust you for not sharing properly? How about just giving the sugar, and you can find harmless ways to prank her later.