Even though Shug has been his lover, and they have had three children together, Mr. ____ is nervous about giving Shug a bath. Celie therefore offers to bathe Shug, and gazes in wonder at Shug's naked body, which Celie finds beautiful, despite Shug's sickness. Shug asks, jokingly, if Celie has never seen a naked woman before, and Celie replies that she hasn't.
Another instance of Mr. ____'s "boyish" squeamishness. Celie realizes in this scene that she is genuinely attracted to women. In contemporary times, Celie's sexuality would be understood to be "bisexual," but at this particular moment, in the South, there was very little terminology in use to describe same-sex romantic relationships.
Shug asks if Celie has children; Celie replies that she has two, but that she does not know where they are. Celie asks if Shug misses her children, who are staying with Shug's mother in an undisclosed location, and Shug answers that she does not miss anything in her life, not even her own children.
Of course Shug later shows that she does have regrets: she apologizes to Celie for running off with Germaine, and for making Celie feel that Shug did not love her. Shug also has an arc of self-discovery, realizing that, despite her desire for freedom, she also has an obligation to those she loves.