Taming shy cockatiel?

[Bird Mom]

So I have had my cockatiel Ellie for years. She is now 9 years old, will be 10 this year. Here's her background story:
I was offered a free male cockatiel by a lady who had 18 cockatiels and couldn't care for them all anymore. When she found out I had so much experience with them she offered me another cockatiel. A female, that I named Ellie. When I arrived at the house I went in to meet the birds. She had two big flight cages which seperated the birds who were related. I guess she had had accidental breedings. Anyways, she told me Ellie liked to be held up to your chin and cuddled. So she took Ellie out and put her in the travel cage I brought. I got Ellie home and realized she wasn't taught "step up" she had always just been grabbed out of the cage. I didn't feel comfortable doing that to her so I just let her be. She is best friends with my other cockatiel Emma who was around the same age as her when I got her (3-4 years old). Anyways, I leave the cage open every day for them to come out, but Ellie never does. She has interest in me she chirps to me and paces like she wants to come out, but just doesn't. Now, she's no where near aggressive. She is one of the most harmless cockatiels, though she likes to act tough. I am able to catch her and hold her, but I've realized she gets very bad anxiety being out of her cage. I have never seen this before. She sits and shakes abrasively and flies around which she also has arthritis in her wings so then her wings her and she probably associates being out with pain. There are occasions where she will come out with emma and join in on some treats but after about 20 minutes she goes back in. Since her anxiety is so bad I will not force her out of her cage, it's her choice. I do believe that at her previous home they were never allow out of their cage so that is probably where it strands from.

Anyways, I was wondering if anyone has any suggestions to make her more tame? I feel if she could over come her anxiety she would be so much more happy and enjoy coming out to be with people.

Again, she is not afraid of me nor anyone. It's not people that give her anxiety, it's only being out of her cage. I made a pvc play gym and if I catch her and bring her out she will sit out on it (with Emma) for hours without trying to go back in. Which is a very good step for her! But again, I don't like catching her. I'm afraid she will hurt her wings flapping them and running away from me in her cage.

[spiritbird]

Can you put toys and perches on the outside of the cage? Then a perch on the inside of the cage door and when she is out keep the door open and stand close to her cage. She may eventually hop on the door perch and go in. You could also temp her with a millet spray just inside the cage door.

[Lady]

I have what I like to call a cage potato. She also doesn't like to go far from her cage. We have a T stand that my husband made for her that we hang toys from and sometimes fruit on a skewer. We keep her cage door open (the whole front of her cage opens) and place the T stand where it extends right above her door. When she's in the mood she climbs right onto it and has what I call special time. If we see her on the T stand we talk to her so excited she gets all worked up, bobbing up and down and at times flapping her wings. We will even put on some "dancing music" and make a fuss to show her that coming onto the T stand is fun.
We did however start out slow by encouraging her first onto the playtop of her cage, then worked our way to the stand.

[Bird Mom]

I put a perch on the door and they have their play gym on the top of the cage. Unfortunatly she doesn't really play with toys. When I got her I noticed they didn't have any toys in their cage so I think she grew up just entertaining herself. She does like her wooden bird kabob. She LOVES millet. I usually feel bad since everyone is out enjoying it and she is just sitting in the cage chirping to everyone so I put a piece in for her. I will try to just feed it outside the cage so it's more special.

[Lady]

Bird Mom, remember baby steps to get them to where you want them to be :).