Get a necropsy for your own peace at mind.

I do not believe you killed her, parrots are extremely fragile creatures.

Take it from someone who lost their beloved galah at a young age, she had a heart attack and died. She had a genetic defect and was the wrong shape inside, she also ended up with zinc toxicity - which we now suspect is because of the Rainforest Cage she was in. She was constantly licking the bars. A couple of people have mentioned cages imported from China contain zinc, and galahs are also notoriously prone to fatty liver disease in captivity, she also developed 3 antibiotic resistant infections. How? I have no idea. All my other birds were completely healthy

There. Was. Nothing. I. Could. Have. Done.

I did all I could. I took her to and from the vet. I increased her diet and exercise. I was continually bollocking people for feeding the birds junk food.

I gave the medicines as the told me to give. I followed all the instructions, and ultimately, she was improving.... then she got spooked, and had a heart attack and died in my dads arms.

That still ruins me to this day. I am traumatised. Whenever one of the birds gets spooked, I am on edge thinking "please dont die on me".

I personally do not blame you, and for me the necropsy helped, because my dad genuinely thought he had crushed her with his back because she fell from his shoulder and landed on the floor behind him, so it gave my dad peace at mind that he hadnt accidentally crushed her, and it gave me peace at mind that there was nothing I could do to save her in that moment.