It takes time and effort to get a chicken to trust you. I think that's what you're experiencing - this hen does't trust humans.
To get her to trust you, it's important to reduce the size and stress of her world. Giving her too much space after being caged likely stressed her out and this could be why she's so flighty.
Try making her world smaller and more manageable. Give her security with cover - a small pen with a shelter with a roof so she feels safe. Then slowly introduce yourself by sitting quietly in her small enclosure with her so she can get used to you.
At first, don't try to touch her. After a few days just sitting with her quietly, bring a treat and toss it to her. Next day, toss it closer to yourself so she has to come closer. Next day hold it out in your hand requiring her to take it from you. But don't try to touch her.
You'll be able to tell when she starts relaxing around you and when you can begin to stroke her neck (never her back) as she takes the treat. Soon she will trust you to handle her, and hopefully, eventually you can trust her to free range again without trying to escape.