Strudel - I think the general concession is if you get another bird, it should be for you, not a friend for your bird...
I do not have a gallah (would love one tho, I love photos of Strudel!!!), but do have the bare eyed (corella) and I'll only be talking about Ivory with this, not Folger who is an entirely different personality. I had always thought I would get another bird, actually I am really fond of a beautiful military macaw at the shelter who is quite interested in me as well. I figured after we move this year if Chyna was still there, I would be adopting him

But I always had a worry about how Ivory would react. She is very much the center of attention for me, she has only recently become more independent and plays with toys on her cage or even go into her cage for a nap. But, she has to know where I am and will follow me most times when I leave the room, especially if no one else is home. And Ivory only is in her cage to sleep or when no one is home, otherwise she is out, Victoria posted the pics yesterday of the flock and the cage in the middle with the boing, perches and large java stand out the side is Ivory's cage. She was so anti cage when she came home that I turned the outside into a playstand so she knew her cage was a good thing! Anyway, I thought that she would be fine since she has plenty to do and I would still be there. But since Folger came home, and we all know I can't play with him, just talk to him... even when I am doing that or we are just laughing at him clowning for us and taking videos, she gets upset. There are a couple videos with Victoria on the floor with Folger sorting items and you will hear Ivory yell in the background and then I move the camera to her and she's doing her batwing show off and such. So at this point, I am doubtful that bringing home another large interactive bird would be a healthy thing for Ivory.
So many people will have different stories and I don't think Ivory may be typical, so Strudel might be very happy to have another bird in the house and not upset that someone else is getting your attention. I am just sharing what we've experienced with Ivory.
If you have a friend with a bird her size that is friendly, I would suggest having a few playdates or even bird sitting for a couple days for a friend and see how Strudel reacts. She may love having a bird around again especially since you mentioned she was housed with other toos in the past. And they are tremendous flock birds, well you live in Australia, I am sure you've seen the swarms!!
Best of luck with your quest, I hope it goes smoothly no matter what you decide to do!! And keep us posted, excited to hear you may get a new baby, while I doubt I'll be adding another too, I can live vicariously thru everyone else!!
