thank you for taking Dewy in. If she is 18 years old and has been treated badly then it will take a lot of time for her to build up trust.
1st of all I assume that you have her in a new larger cage?
You must give her time to adjust to the new home... all is strange..
cage, surroundings, sounds, you and toys.
I would put a chair next to her cage sit there and talk to here, read a book out loud just so she can get use to you.
Does she talk?
I would offer her a treat when she responds in a positive way to you.
How many in your family?
Any children?
Dogs, cats or other birds?
She will have to adjust to everything.
Just be patience and She should come around. Greys are great Fids..
Ask Ant, and Spiritbird and Graycloud, they are guardians for Greys.
I hope this helps...