Katie Cassidy is nothing like her devious character on the CW’s recently canceled “Melrose Place.” Cassidy, who is currently filming the new “Nightmare on Elm Street” with Kellan Lutz, is working with Malawi charity HELP to build a library for a group of remote villages. She has persuaded the hospitality company the Light Group to donate $15,000, and its president, Jodi Myers, will hand over the check tonight at Bank Nightclub in Vegas.