Baby Diagnosed With Milk Allergy, Having Fever, Vomitting Yellow Colour Liquid. Suggestions?

My 2 year old was diagnosed milk allergy , don t know how far it s true but she is happy eating yoghurt from cows milk, before she was diagnosed she stopped taking liquids and solids for 1 to 2 days a month since she was 1 and half year old , when she was 1 year 10 month ahe was diagnosed allergy, and she use to vommit in the night sometimes only the phlem and suffered with severe diarrhea , and her stool use to stink a lot. She suffered for almost a month, and gine down in weight too.Now she is 2 years 3 months, and she is suffering with 101celsius fever and vomited some amount of yellow liquid, so wat could her problem really is,