She's a star witness because she's the only witness to contradict George Zimmerman's claim that he stopped following Trayvon Martin. The defense suspects she's making this all up-- that she had nothing important to tell police, which is why she never bothered contacting them.
At some point, weeks later, the Martin family contacted her. She now explains her failure to step forward with critical information in a homicide case by saying she expected police to contact her, because that's what always happens on First 48 (one of those crime documentary news magazine shows).
"Don't you watch First 48?" she asked a defense attorney when pressed on this claim. As if she thought the attorney's knowledge of police procedure came from the same place hers (allegedly) did.