If you haven't been posting on the Allergies forum (in the Health and Healing section), definitely head over and introduce yourself, because you will find a lot of BTDT moms there, dealing with allergies/elimination diets!

C'mon over, introduce yourself, read some of the stickies and threads and lurk a bit and you will find all sorts of information and support.
What the research shows is that breastfed babies have fewer allergies than formula-fed babies. It's entirely possible I suppose that formula-fed baby could not manifest allergies until their diet diversified (unlikely since many babies' primary allergies are cows milk or soy) - but that wouldn't mean that the allergy wasn't going to manifest.
If your little one had been formula-fed, I can tell you that you might have really struggled to find a formula to feed her -- after all, formula is made of cow's milk, soy, and/or corn syrup solids. My dd1, who had to be supplemented with formula for awhile (long story involving reflux, retained placenta, poor latch, and allergies) -- could not tolerate the 'hypoallergenic' formulas, although she could tolerate Neocate (an elemental formula which is very expensive). I had friends whose babies couldn't tolerate Neocate, either -- their babies were in a constant state of low-grade reaction etc. Six years ago, Neocate cost us $15/day when dd1 was on it exclusively (around 3 months of age). Families go bankrupt paying for these expensive formulas. You are very lucky you were breastfeeding, and that you have fought to continue breastfeeding despite these challenges. I was really glad when we were able to return to 100% breastmilk.
In terms of outgrowing allergies at a year of age - many babes do outgrow within that second year of life (purely anecdotally it seems like sometime between 15 and 18 months among many of the moms in my support group, for dairy/soy) -- something like 85% of infant allergies are outgrown by 3 years of age. So, some can and do persist. Dd1 outgrew all her allergies before 2 years of age, other than egg (which persists to this day) - she was allergic to dairy/soy/egg/wheat/legumes as an infant and we avoided fish/shellfish/peanuts/treenuts 'til she was three as a result. Dd2 outgrew her allergies (dairy and soy) before she was three.
If no one has mentioned adding a dairy/soy free probiotic to your diet and your dd's diet, definitely consider it. In my opinion, it's been the difference between my dds' allergy severity/number/duration. Something to read up about when you get to the allergies board. There is some research which shows that some mothers of food-allergic infants have more intact-ish proteins from the foods they eat in their milk - the probiotics help with digesting those proteins into smaller bits that are less identifiable (and, again, formula IS those proteins - cow's milk, soy, and corn involved, so it wouldn't matter whether you were breastfeeding or formula-feeding if an allergen were involved, babe would react).
Kudos to you for sticking it out - breastfeeding on an elimination diet is difficult, and it takes a lot of work and commitment especially when your support system is telling you formula is better (I had a lot of that 'helpful' advice with dd1 too

).