I'm going to lie to my friend.
Is there a reason for lying to her?
It's because she's an idiot. And she's annoying when she doesn't understand what I say.
Regardless of her intelligence, you are still her friend. Lying to your friend for something she can't really control is wrong. Try communicating in a different way with her instead.
I was joking, you took this too seriously.
You are the one who asked me for advice.   I think that not being truthful adds drama that is not necessary.