Exactly what Jo said. She sounds stressed, so its best to earn her trust by letting her come to you for treats. She will associate you with yummy food.

Instead of taking her completely out of her cage for minutes at a time, You can pick her up, try not to hold her, but let her walk on your arms for 5 seconds or so, and let her walk back into her tub. It will teach her that she can get back to safety of her cage, and you arent all that bad. From there, its just about increasing the time out of the cage, and being able to see when she is stressing and wants to go home.
She may never be very outgoing, but it's a relationship, slow persistant work and trust building is key.