Why does Hester dress Pearl elegantly?

I think that Pearl is the one thing that Hester is not ashamed of. Despite the town's gossip and judgment, Pearl is the creation of two people who are in love (Dimmesdale and Hester). Where Hester must hide because of her sin, Pearl must be celebrated for the Purity of love. It is this paradox that Hawthorne wishes to highlight. Hester is saying, not so subtly, that Pearl is her treasure despite whatever "sin" she might have committed.

Pearl is the walking representation of Hester's sin, and because Hester realizes that she is not the only one who has committed sin, she dresses Pearl to almost mock her punishment. If Pearl is, indeed, a "devil baby" as she is described in the novel, what better way for Hester to fulfill her obligatory punishment than to dress Pearl elaborately--a direct contradition of the Puritan code that expresses dictates a plain lifestyle.