To me I see a disturbing sexual connotation to this line that Nettie seems not to notice this. In a world full of such misogyny, it seems that Nettie has retained her innocence.

Even a christian women believes that worth is only as a mother and wife. Nettie is fighting the idea that she is worth nothing by herself, she is facing the patriarchal ideals prominent in Olinka.

To the people of the village the very roof on their head became the thing they worshiped. It is what keeps them safe, shelters them from the harsh world. Without the rootleaf, they would die like many of the other villagers have. This is similar on how the Christians rely on Jesus.

Nettie continues to write letter even though they won't reach Celie. She compares the feeling of not writing to her to god, which shows how much Celie means to her. She continues to write even when she knows they won't reach her, maybe for herself because she has done all she can to reach Celie like how Celie does with god.

Why does the mayor buy his wife Millie a car if he won't teach her how to drive it? Maybe he does it to show that she isn't inferior to a "person of color" but doesn't want to give her the power of independence.

Here we are introduced to the character Shug Avery. Later Celie meets her and she i seen to be a nasty person yet she idolizes her. Why is it that Celie has kept this picture? The moment she was given the picture, Celie fell in love. Does Celie idolize her beauty, or is it something deeper? Perhaps she fell in love with her eyes, eyes that have been through abuse and hardship. In the book, everyone who has a "women's eyes" is given a name by Celie. Harpo is given a name and we can see him start to change when he is faced with hardship, being forced to work by his father. Maybe she understands Shug Avery's struggles and idolizes her for her strength to push through abuse and discrimination, obtaining success in a "man's world".