The answer to this question can be found at the end of Chapter Eleven. This is when Tea Cake says to Janie the following phrase:
Janie, Ah hope to God may kill me, if Ah'm lyin'. Nobody on earth kin hold uh candle tuh you, baby. You got de keys to de kingdom.
Tea Cake is paying Janie a massive compliment here. The metaphor of "de keys to de kingdom" suggests that Janie has access to the celestial kingdom of heaven. It is important to realise that this comes at a point in the story when Janie has reached true happiness and has found her own identity and she is able to express that identity in a loving relationship with Tea Cake, who allows her to be herself and does not try to control her like her other two husbands. It is tragic therefore that this declaration of what a wonderful woman Janie is comes just before the end of their relationship through Tea Cake's death.