If you listen to her, she presents the information but she couches it as possibly completely false- she actually points to the Smarts' father as initially a person of interest but completely innocent. She also talks about "the last person to see the missing" as always the initial focus of investigators because well... what was the missing person's mood? what was she wearing? what did she say? etc. etc. So while she presents this info as a potentially big thing, she backtracks on it too. (Just thinking about this, suppose NG had a blister or a cut already in the car on the way home - would that make the blood drops not a sign of an attack? I personally doubt this but just tossing it out as how important what observations the last person or people to see a missing person could be.)