Nel and Sula’s friendship is central in the novel. What role does this friendship play in Nel and Sula’s lives and what point is

Hello writer,

I attached the instructions for the essay it’s a literary analysis about the book Sula by Toni Morrison. Please focus on the topic that I chose.
The professor asked us to choose two articles that were in the school’s system.
If you want to have another source it’s okay too.
Thank you so much. I hope I gave you enough time.