Did the man bring the food she was used to eating? If not, did you get the name of the food? Some birds don't realize that a new looking food is still food. Even if he was using a not so fabulous food, she may need the same food for now and to be gradually switched to a better diet.
Have you tried thawed frozen mixed veggies? She may not be familiar with them but most birds like the corn and even though it's not a complete diet, it will keep her from starving and has lots of moisture in it.
I think she may just be very cautious around you since you are a complete stranger. Your mannerisms are so different and your voice is so different. An example is my sis in law. She talks in a falsetto voice to my birds instead of her usual deep voice and it scares them. She won't listen to me when I tell her to use her normal voice.
Have you tried sitting quietly by her cage, not looking at her, and reading the newspaper out loud? It will help her to realize you won't hurt her and she will get used to your appearance, your voice and your movements.
I feel sorry for birds who change homes after so long with a first family. I worry about mine in the future when I can no longer care for them.
I sure hope you can find a food she will eat.
If her perch is up high, get a small clip on or screw on bowl and put it up where she sits. I would try anything to get food into her.
Annie