Meaghan Martin (“Camp Rock,” Mean Girls 2″) leads the cast of “Red Flags,” a darkly-comic erotic thriller now in production along the Algarve coast in Portugal. The U.K-Portuguese co-production marks the debut feature of writer-director Bradley Porter, based on a story developed by Martin. “Red Flags” follows a former child actress who husband disappears on their European vacation, triggering what the synopsis describes as a “ravenous journey of self-discovery driven by an insatiable appetite