What do you actually mean by unified? Do you mean coherent or that it holds together? Certainly, if that is what you are asking about it is clear that this chapter is definitely "unified." Note how it begins with a description of the family's different hair types and then ends with the fragrance of the narrator's mother's hair that brings forth such a rush of fond memories for her. It is unified in retaining a focus on the subject of the vignette, "Hairs," as the title suggests, and elaborating on that theme. Note how the narrator classifies her family by their hair types:
Everybody in our family has different hair. My Papa's hair is like a broom, all up in the air. And me, my hair is lazy. It never obeys barrettes or bands. Carlos' hair is thick and straight. He doesn't need to comb it. Nenny's hair is slippery--slides out of your hand. And Kiki, who is the youngest, has hair like fur.
Thus the unity of this vignette is based on the way that it remains focussed on a common theme and how this theme is elaborated throughout the vignette. Cisneros never strays from this theme, and, as noted, the vignette or chapter begins and ends with the same topic.