Beth Palmieri aka: Lizzy Walker was the villainess of "The Lost Girl", the 3rd book in R.L. Stine's revived Fear Street series (published on September 29, 2015).
Born in the year of 1950, Beth was the daughter of Angelo Palmieri, a former stableboy who was on the verge of opening his own stable. He was the former employee of Martin Dooley, whose nephew Aaron endlessly harassed her due to being attracted to her. In the opening, Beth was attacked by Aaron. It was then that she used her secret psychic powers to choke Aaron. After a few moments of enjoying Aaron's struggle, she let him go free.
Later that day, after Angelo refused Martin Dooley's demand to close down his stable and go back to work with him, he had some of his men attack and kidnap Angelo, with Beth following them without their knowledge. When she saw them tie Martin to a pole and cover him in oats for the purpose of feeding him to the starved horses, Beth tried to use her powers to save her father, but she was unable to and watched in horror as her father died. When the men and Aaron (who was present as well) saw her, Aaron chased her into the forest. Unbeknownst to Beth, Aaron was trying to save her. Beth went into a cave to hide, which turned out to be a portal that sent Beth (and later Aaron when he went in to find her) to the future. After finding Michael Frost, the grandson of Martin Dooley, Beth and Aaron (now lovers) plotted to get "by proxy" revenge for what happened to Beth's family.
In the present day, Beth adopted the name Lizzy Walker and first interacted with Michael in a grocery store when he caught her stealing food. The two quickly became friends, much to the annoyance of Michael's girlfriend Pepper. Beth showed a sign of Michael's true form by doing a "blood brothers" ceremony to Michael at school by pricking his finger with a thumb tack. During a snowmobiling trip with Michael and his friends, Beth used her powers to make it appear that Michael hit a man (later revealed to be Aaron) while claiming he was an unstable classmate from her previous school named Angel. She and Aaron then began attacking Michael's friends, with Beth faking her own attack to make herself appear innocent. Their assaults included tearing out some of Pepper's hair and tying Michael's friend Diego into the boiler of the school, burning much of his back.
The evil couple also drove Michael's car off the road while he was driving with his friend Gabe in the car, resulting in Gabe's death. It was after the accident that Michael uncovered Beth's secrets, discovering that she was not registered at Shadyside High and discovering her picture in an old yearbook. Beth made her villainous reveal when she had Michael meet her in the Fear Street woods to kill "Angel". Pepper followed Michael, angering Beth when she arrived. After using her powers to freeze Pepper, Aaron appeared and Lizzy revealed their intentions to kill Michael. The couple led Michael to the cave, revealing her connection to Michael and how she wanted to get revenge for the suffering Michael's grandfather caused her family. Beth prepared to force Michael into the cave, which would send him back in time, potentially to a time period where he wasn't born. But as the three went into the cave, Michael fought back and pushed Beth and Aaron back into the cave, causing them to rapidly age until they were nothing but skeletons.