Welcome to Health Care Magic Forum,
yes i think you are in right track if doctor feels its typhoid
but cant confirm and say it is till test comes positive but its wise to continue antibiotic till then. Typhoid takes a long duration of time to fever
to decrease. But if vomiting
is not improving then other causes should be ruled out. But make sure she takes adequate fluids and the diet you mentioned is good enough.
Hope she gets well soon