Hi A.,
Well I agree with alot of what the other moms were saying. I don't believe your daughter has an allergy to your breastmilk, I think it's more in the form of maybe what you are eating.
I don't understand why they went right for soy formula when there is plenty of milk based formulas to try. One of the reasons why she may not be eating is because her formula isn't warm enough, think about it she is used to drinking from your breast and think about the temperature of what it probably is. The other thing is that the taste of breastmilk and the taste of soy formula is totally different.
Also the amount a baby can eat can vary, for instance...I have 4 children and the oldest would drink 4 ounces every 2 hours and never went over that. My 2nd would eat 6 ounces every 4 hours. And my 3rd would eat 8 ounces every 3 hours. And my 4th daughter was eating 8 ounce bottles every 4 hours. So if you do the math for my 4th child she was eating 48 ounces in a 24 hour period and this is at 3 1/2 months old. My 3rd daughter was eating this much at 2 months old. So like I said it can vary fron child to child.
I think I would do a little more research on the formula/breastmilk situaton and also move towards milk based formulas ( you may have to try a few different ones before you find the one that works.
For instance again I have a friend who had twins the same age as my 4th daughter and they couldn't handle the Enfamil Gentlease or the regular Enfamil so they finally found that Carnation good start worked best (after she gave it her best effort to breastfeed). My daughter counln't handle the regular Enfamil but she could handle the Enfamil Gentlease.
So go with you gut, see what you can find out on your own. A pediatrician only knows our children by what they read in their chart. They don't live with each of our children each day like we do, W.