Not much is known about Star; one can speculate she was a runaway that eventually met, and fell in with, the Lost Boys. A common belief is that David recruited Laddie when she wanted out, as a ploy to keep her in the gang. Fans speculate that she was David's former girlfriend before Michael, despite David showing little interest in her thoughout the film, sleeping away from Star and ignoring her presence; the only scene in which they interact is when David exercises power over her choices; it implies posessiveness as opposed to a sensual or romantic subtext.
The Lost Boys
Star is the mysterious girl that catches Michael's eye on the boardwalk. (It is arguable that Star was "bait" to lure Michael.) Over the course of the film, it becomes clear that Star is trapped in the dark world of the Lost Boys, and longs for escape along with Laddie, her younger friend. She offers solace to Michael in his confusion about being a half-vampire, and they wind up being intimate. They fall in love thoughout the course of the film, coming together finally when the curse is lifted and Star, Michael and Laddie are cured.
Lost Boys: Reign of Frogs
In the comic, Edgar Frog states that Star and Michael were killed in a car accident, but was apparently a fabrication on Edgar's part as he was threatened by a vampire at this point. Although speculation led fans to believe that Michael and Star were the parents of the siblings Chris and Nicole Emerson who also lost their parents leading into the events of the second movie, however the official website of Lost Boys: The Tribe confirmed Chris and Nicole as cousins of Sam and Michael Emerson.
Lost Boys: The Thirst
Edgar Frog attempts to recruit a non-willing Alan Frog - now half vampire - in helping him in his mission to hunt the alpha vampire. When Alan suggests asking for Sam's help, Edgar mentions that Sam had turned vampire and 'he did what he had to do,' also stating that he was ex-communicated by the entire Emerson family for the incident when Michael and Star's names are brought up.
Beautiful, mysterious and somewhat melancholy; Star is the girl who captivates Michael on the boardwalk on the fateful night he first sees the Lost Boys. Star is quiet and awkward, lingering in the background with a tense knowingness. She is gentle and reserved; demonstrating a maternal side with Laddie, which confirms her lingering humanity. Passive, caged and trapped in her own personal hell by The Lost Boys; she seeks salvation with Michael. Though she shows steel when protecting Laddie or facing up to Max, she is powerless in her scenes with the Lost Boys, despite her attempts to discourage Michael from drinking from the bottle. In the same scene, everyone is provided food except her. We never see Marko offer her any, or see her refuse; we just see that all the boys are handed Chinese but not her, and she doesn't speak out about it or make any effort to claim some food. This suggests that her strength has been beaten down by fear. An example of this is when Star is about to "go for a ride" with Michael. David stops her with merely her name, a warning clear in his voice. (The implication is clear; go with Michael and I'll kill him.) By her own human heart, Star is completely in the Boys' control. Hopefully, with her liberation from her status as a half vampire and new relationship with Michael, she can grow in confidence and her faith in her own strength or sense of self worth.
David: Star's relationship with David is left ambigious for the most part, but is shown in the film as platonic, but bullying and possessive. David offers Star no authority over her own choices and merely delivers tolerance and indifference as the sources of his main attitude towards her. (It could be argued that David may keep her in the gang largely as bait to draw in potential new members.) A romantic connection is spoiled by the fact that David shows no feeling over Star's growing love for Michael; he allows them to be together if it only means Michael is initated into their gang. Out of spite, he tells Star to make Michael her first kill after their first meeting, but judging by his changed attitude towards Michael during the film, he forsakes this plan of action (with of course, Max's plan as well.)
Laddie: Star has taken the role of his protector and relates to him as a big sister or mother figure. She shows her greatest determination and strength when defending him; she insists that Michael take Laddie out of the cave before her, and she steps between him and the Frog Brothers even though Laddie has vamped out and appears at his most dangerous. Paradoxically though, this also highlights her submissive quality, as she is more willing to stand up for a child than for herself (a traditional female role).
Michael: Star's attraction to Michael stems from a mixture of impulsive affection, and a need to connect with a form of humanity. During her talk with him on the boardwalk, one can assume she has attempted to remove herself from the boys in order to spend some time with him (or, on a less generous level, bait -- willing or unwilling is debatable.) However, she does look sincerely angsted at the Boys' arrival. Her feelings and concern for him are strong enough for Star to uncharacteristically step out of her aloof, fearful persona to warn him about the blood (even to meekly scold the boys at their teasing of Michael.) Upon his initiation, their relationship takes a new turn. Bound together in a horrid half state, Michael can relate to Star in a way which excludes Sam, Lucy, or other close members of his family or friends. This deepens their bond almost instantly, leading to Michael seeking solace from Star. She initiates physical intimacy, which not just acts as a confirmation of their attraction, but a desire for comfort and a weak replacement for their budding blood lust.
Later, after the campfire scene, Star meets Michael at his home in a plea for help. She claims to "care" for him, but is angrily rebuffed by a disturbed, hurt Michael, who laughs mockingly at her request, causing her to leave. The behavior here is strictly different from earlier, tendered encounters; one can speculate Michael felt that Star was merely using him as a way out of her hell, and lying about her feelings in order to accomplish that. However, he seems to drop this assumption, calling for her after she leaves.
The next day, Michael goes to retrieve Star and Laddie from the cave, showing his love for her hasn't changed. After David's death alongside the shock of them realizing their vampirism hasn't been cured, it is Star Michael pulls to him to shield himself from the others. She comforts him in this moment. Later, after Max's demise and the restoration of their humanity, Star and Michael embrace, their nightmare finally over. It is confirmed in the third film that they are still alive, and most possibly, still together.