I don't know what you've tried already but like someone else said fess baby drops are helpful (tho they hate them!)
-Feeding with baby upright is brilliant when has a cold especially sore throat.
-Also are you using lansinoh at all? It really can work wonders!
-If supply is bothering her try breast compression during feeds or even expressing until getting a let down. (& even 10-15mins after feeds if u can find time to get another let down).
-can try feeding bub in a dark quiet place when sleepy/asleep.
As u can probably tell I've got some experience with fussy babies & supply! HTH a little... The hardest thing is just relax as much as possible u will get through it