Shopping can be dangerous!

Elizabeth Wakefield and her friend Maria Slater are filming at the Valley Mall with Maria's new video camera when jewelry store is robbed right in front of their eyes! Elizabeth can't believe the criminal escaped in broad daylight through the crowded mall. She and Maria decide it's time to start investigating.
Soon after, the stereo store and the camera store are robbed. Elizabeth is desperate to crack the case. If only there were a clue . . . Then Maria's house is robbed and their entire collection of video tapes is stolen. Why would anyone want Maria's home movies? Finally Elizabeth thinks she has her clue.
Have she and Maria held the key to the mall mystery all along?

Who dunnit?

At the sound of smashing glass right behind her and the earsplitting alarm, Elizabeth spun around. It took her a few moments to focus on what the problem was. Her mouth dropped open as she realized that the display window of Precious Stones had been broken. A young woman with a baby carriage was staring in shock at the store window.
"Maria, look!" Elizabeth cried, already moving forward. Maria was right next to her, her video camera dangling at her side.
"What happened?" Maria asked. Then the two girls were surrounded by people swarming over to the sound of the alarm.
Staring at the jewelry store window, Elizabeth saw that the expensive gold watches, rings, and necklaces of the display window were gone.
"It was a robbery!" she cried.

Who's the mysterious new boy in Sweet Valley? Stevens Enemy