Don't be discouraged. You're learning! We all had to do it at one point in time. You opened your heart to her.. Give it time.. She's opening her heart to you too! It's only been a few days and she's still trying to figure out what's going on.
If you were a 3 year old child just dropped into a completely new situation, you'd be completely freaked out too! Especially if you were in a "not so savory" environment and stepping into a new one!
Just give her love.. Take her around with you.. show her love.. try hand-feeding her food and water! It really makes a difference. My little guy (Duke) isn't eating as well either, but all I did was hand feed him, give him tons of water and spend TONS of time with him. He spent 6 hours on the back of my chair today. He is only starting to eat a bit more. He still won't eat in front of me, but he is purring when he's with me.
Try giving juicy foods with liquid (like oranges). The change in diet is going to be a stress to her, but she WANTs to eat it.. Her body just isn't accustomed to all the new nutrients and good food!
As for the feather thing.. Who cares! Do you love her for how she could possibly look? or do you love her for who she is? You didn't rescue her because you wanted a new piece of art in your home! The other birdy loves her! She just needs stability and reassurance and feathers or not, she's going to be the most beautiful birdy in your heart!
A bird like a macaw really needs ONE human mate. Everyone else, they tolerate. If you're that one person for them, then let her get the opportunity to "decide" to choose you! It will take gaining her trust first!
After that, she's going to see that you're her forever mommy and the rest will be history!
When you've been treated like crap all your life, it's hard to believe there is good in the world. Not just from a bird's perspective, but from a human perspective.. I know that one personally..
Give her time and don't be deterred! I don't know many bird owners that would take the multi-hour drive, because you were worried! There are some that will just say, "oh.. the vet's not available.. I'll wait." and let the bird suffer until it's convenient for them.
You have my respect and I'm sure the respect of many others on this forum for doing what you did. That's what makes you a good bird owner.. the skills and experience will come in time.. It's the persistance and dedication that is hard to find.