How do girls reply when they say they are joking?

You can reply to her. Are you kidding? If she says yes, you can say, I'm joking, you're joking, and then you two can have fun together. If she says no, you can say I'm joking, and you can reply that I'm joking. Then you can have fun with her, so that you can reply to the girl that she is joking. You can say, are you kidding? If she says yes, you can reply to her. I'm kidding, and so are you. That's it. You two can have fun together. You're kidding, too.