How do I get this kitty to trust me?

Unless she has a collar she's probably a feral, and because she's a full grown cat and not a kitten, it's going to be a lot harder to get her to trust you. Don't trap her! She'll just freak out and be even more scared of you. When you bring the food out, try to stick around until she comes. If she ociates you with food, she'll probably start to trust you more. Don't try to approach her right away either. Just sit there and watch her eat, but close enough so she can see you. That way she'll start to recognize you and will realize you're not going to hurt her. Once she starts to get used to you being there, try to get closer and eventually feed her out of your hand. This won't happen overnight or even in a week or two--since she's a full grown cat it's going to take a while. If she does eventually let you touch her, don't pick her up right away either. Just pet her and scratch behind her ears--cats love that. Just take baby steps and eventually she'll come to trust you.