Beth was killed while riding a Ferris wheel at the state fair; she said the teenager who was running it allowed her to go an extra turn. Prior to her death, she had checked a box on a form that allowed her body to be used to test automobile safety in the event of her death.
When Mark Chase, president and CEO of Dandy Lion Worldwide Enterprises started using cadavers instead of crash test dummies to conduct safety tests on the Dandy Lion SX, in order to avoid capturing electronic evidence of defects with the car, Beth's body was one of the cadavers selected. 
Although Chase had already committed murder in the past for the protection of his company, it is unclear whether Beth and the other people used as human crash test dummies were killed by the company or not; the fact that they volunteered their bodies for such research indicates they may have simply been provided to the company following their deaths. 
Behind the scenes
Beth is never referred to by name during her brief appearance on the show.