Catsu how are you getting on?
The helplines run by NCT and the Breastfeeding Network are impartial (i.e. no involvement with formula companies) but as tiktok says, serious allergies and intolerances are out of their remit and they are likely to signpost you to a medical professional.
My own DS has multiple food allergies, and I do know that it can be very difficult to get impartial breastfeeding advice in our situation 
The current NHS/NICE guidelines recommend that breastfed children who have allergies should continue to be breastfed if possible, and that their mums should be given information about exclusion diets. However, in practice, this information is rarely given. Most 'frontline' medical professionals simply do not get enough training about allergies.
I found that a number of HVs, two GPs, the hospital dietitian and a paediatrian specialising in allergies all assumed that I would not be able or willing to cut all the offending foods out of my diet. I was offered hypo-allergenic formula for my DS countless times, and when I insisted that I preferred to breastfeed, I was twice encouraged to take free samples of Neocate away with me for when I changed my mind!
It's worth noting that many of the leading medical professionals in the allergy field give lecture tours which are funded by the companies which manufacture the hypo-allergenic formulas... no wonder that so many medical professionals see specialist formulas as the 'answer' to feeding allergic babies...
It is perfectly possible to breastfeed a baby with allergies - I have done it! I do find it very hard to control my own diet, but I see this as good practice for balancing my DS's diet. Have you thought about keeping a 'food diary' with details of what you and your baby eat, along with any symptoms that she develops? This might help you to pinpoint what she is reacting to.