The first issue we need to look at is the nature of "The Odyssey" as a poem. Most modern scholarship agrees that it was composed orally for oral performance, and did not attain the fixed form in which we encounter it until fairly late in its history. Instead, the various stories of the events that occurred on Odysseus' return from Troy were sung in various different forms, sometimes as large narratives and sometimes as individual tales, with the singer adjusting the shape of the tales and the episodes included to suit the particular audiences of the moment. For such a type of work, the modern concept is thematic unity is really not applicable; as in the picaresque, tales were included if they made good stories, rather than as part of some overarching narrative arc.
Nonetheless, the Nausicaa episode is typical of many of the themes we find in other parts of the Odyssey. Three other episodes center around women met by Odysseus, ones involving Circe, Calypso, and the Sirens. In all three cases, the women serve as obstacles and challenges to Odysseus in his efforts to return home. Nausicaa, however, is similar to Penelope in being a woman set in a domestic role who actually helps rather than hinders Odysseus. Thus she is an appropriate transitional character between the "women-as-obstacles" and "woman-as-ultimate-goal."