As the article further notes, the only question is whether a loophole in the law's definition may cause Ms. Fong to not qualify as a car rental entity.
I did not click through that law, but only read the (emphasis added) "In any event, she has done her own legal homework and points to a federal law that can shield rental car companies from liability for accidents that happen while someone is renting the car.", and concluded (possibly incorrectly) that that law isn't watertight.
Well, it is that clear cut. As the article notes there is a law which unambiguously states that car rental agencies are not liable in this scenario: http://gregjohnson89.wordpress.com/2010/10/28/vicarious-liab...
As the article further notes, the only question is whether a loophole in the law's definition may cause Ms. Fong to not qualify as a car rental entity.