Why would Pearl not cross the brook and go to Hester?

This chapter is highly symbolic of the spiritual relationship between the three characters involved. Pearl refuses to cross the brook until Hester puts the scarlet 'A' back on her chest. Pearl demands it--even to the point of throwing a temper tantrum.

I think that Pearl has grown up with her mother wearing the "Letter" on her. When she sees her mother across the brook with her hair down talking with a man (Dimmesdale), Pearl is apprehensive. Hester is undergoing a transformation of sorts and Pearl is not used to this.