So after Halloween 4 set up Jamie as the new killer... then.. Halloween 5 set up Jamie as the psychic girl, Halloween: The Curse of Michael Myers set up Jamie as a mildly important but mostly disposable character so we can get to the REAL important details! Which still aren't (blog post) quite hammered out, don't make sense, and differ (blog post) depending on which version of the movie you watch. What fun!
Source: Halloween The Curse of Michael Myers Movie Review - Decker Shado