Sula sleeps with Jude in part to avoid her hell which was sameness. She is afraid of things staying the same and this for her characterizes what she would consider hell. Jude is something new and different and therefore she sleeps with him. She leaves him for the same reason. He is no longer something new and different, and she fears what might happen if things begin to stay the same.
Nel was devastated when she discovered Jude and Sula but she does not cry. A possible interpretation for this might be that since her idea of hell is change, she has now seen hell and discovered it is not as bad as she thought. She loved Sula and enjoyed her company so there is an element of double betrayal here. She is rendered at least for the moment unable to speak.
This is the only chapter where humour is used. Sula's and Nel's memories woven together in a funny way and their joint laughter are powerful tools the author uses to highlight the impending tragedy. Even the scene of Nel's catching her husband and Sula as retold through her eyes is humorously done.
In the scene where Nel discovers her husband with Sula, Morrison creates a powerful image that would ordinarily be somewhat humorous, is breathtakingly tragic when told through Nel's point of view.
Quotes cannot be included as there as word limit. See link below.