New cat, help! *Update*

*Update in comments * So I recently adopted a new cat, a 5yr old mix called Ori and she is incredibly shy! She'll hide with any loud noises and can't handle sudden movements. I've given her her own room, with a cat bed (Loads of blankets, including her old one), scratch posts and a place to hide in, litter box, toys, food, Feliway pheromone releaser (To help relax her), so everything I can think of! My house is quiet and I try my best to be as gentle as possible with her. I know she has been incredibly mishandled in the past. So, I'm just wondering if anyone has any advice on what else I could do or how to help a cat like this.