E Coli is everywhere and many many different strands. It is apart of our intestinal flora. I am sorry Coco is ill. It is so hard to sit by and watch those we love having problems.
I am sure your vet has prescribed stuff specifically for bird intestines to help prevent further irritation. Just like with people, the lining needs to recover. In people it can be a few days to a week. The intestinal walls have a relatively fast turn over and slough off routinely.
I would want the vet to find out what adhered to the wall and make sure it has passed, whether it is parasitic or toxic. I think just giving the most gentle of foods, staying away from nuts and seeds stuff like you would a human. Possibly provide probiotics to help in healing the intestinal walls.
Hydration would be important. This is very different, but when my B&G went off food and fluids while she sat on an egg, I tempted her with juice. That got her interested, but in this case, I am not sure what kind of juice would irritate her gut the least amount.
As far as the future diet, I think only time can say if there is scarring/lessions that would be a future problem.
Oh crap. I just looked up and read that her bowel did in fact rupture? It is risky. The infection needs to be resolved prior to any healing. darn it.
I am sorry. I do hope Coco comes around soon.
sherri