It's like she was being chased by the Boogeyman, Oda adding her attacking Garp just to do nothing was purely to dunk on her in favour of him. There's no other context. That is the context. She is not just running away while laughing, she is soiling herself after witnessing what just happened. This is not a gag, it's establishing hierarchy.
I'll repeat if Rayleigh got a scene like this, he would never ever be able to recover from it. It's insane to even imagine it.