Sweet Valley High/WMG

The Amy Sutton from Sweet Valley Twins and the one from Sweet Valley high are different people.

 * The books have a lot of girls that look just like the Wakefield Twins and pretend to be them on occasion (Margo being the most notable example). Who says that only Elizabeth and Jessica get doppelgangers? That could explain why Amy underwent such a drastic change between the two series. In Sweet Valley Twins, she's a smart and lovable tomboy and the loyal best friend to Elizabeth. In Sweet Valley Twins, she's a shallow, boy crazy bitch. Maybe somebody (Margo?) found a girl who looked like Amy and sent her to Sweet Valley to spy on and take down the Wakefield twins. It didn't work because the replacement wasn't very smart and was more interested in hooking up with hot Sweet Valley guys.