I saw your post and just had to respond. My 2 1/2 year old son had the same milk protein allergy that was diagnosed when he was 6 weeks old because of blood in his stools. The pediatrician told me to stop breastfeeding at once because they weren't sure if it was something I was eating. They told me to "pump & dump" or to "pump & freeze". I tried a couple of times, but I just didn't have time to do either since my husband was deployed with the military at the time and I had no help with the baby. And I agree - the diet is very restrictive for the bf mother when your baby has this type of allergy.
Like you, I always had to supplement my son's feedings with formula. Even though I pumped 4 times a day and tried to nurse him at least 3 or 4 times, I just wasn't producing enough milk, so I sort of gave up after his diagnosis. It was the easiest thing to do since I was acting as a "single mother" - because of my husband being gone. I wish I had been more persistent and maybe sought help from LaLeche, but luckily, he's a healthy, brilliant, active 2 year old.
He was allergic to soy, too, so they put him on Nutramigen formula (made by Enfamil). It is really expensive and I didn't find out that my insurance would pay for it until I switched doctors when he was 6 months old. That is something you should look into. I'm not familiar with Neocate, but your insurance should cover a formula if there is a medical necessity for it.
I hope your daughter is doing better now. And I hope you're hanging in there with the breastfeeding. :)