Shug is a positive influence on Celie. Helping Celie to open herself up to love and real affection, to achieve a new and empowering relationship to her God, and to grow into a confident woman who values herself.
All of these changes in Celie are critical to her psychological and mental health. The results of Shug's influence on Celia are clearly beneficial. However, we may question the realism of the relationship.
Is it realistic that a childish crush would develop into a mature, loving relationship? Considering the (harsh) details of Celie's life with Mr. ____ and her step-father, is it contextually realistic that Celie's life with Shug should be sketchy and vague, presented with few details? If Shug is so wild and free and bold, is it realistic that she would settle for such a meek figure as Celie, especially considering the preferences for strong men?
These questions are only somewhat valid, however, as this novel is not a work with an emphasis on realism. The emphasis is on theme and sentiment. The social content of the novel is entirely in keeping with the relationship between Celie and Shug. This relationship explores self-acceptance as a basis for love, addresses the fallibility of love as a permanent bond, and helps to develop the protagonist into a model figure of moral growth.