My baby refuse eat any or has an advice

My baby recently turned 4 months and a week old she doesn’t want to drink her formula unless she is about to sleep or take a nap the most she can drink Is 4 oz and that’s if am lucky because she refuses to eat I started thriving her rice cereal which she loves by the way since I can’t watch her go hungry all day without any food . She is allergy to cow milk so she is on nutramigen which is bitter to taste. Does she refuse to drink cause she hates the taste now or cause she still has mucus in her throat which I have tried my very best to let it subside. I need you advice my family