The red throat, associated with cold
of voice is commonly seen in laringitis,I feel she should have been given adose of antiinflammatory drug lke Ibuprophen-paracetamol-serratopeptidase combination & antihistminic like cetrizine
along with antibiotics. cough syrup & B complex suppliments would benifit.
In addition, avoide sour,cold & oily eatables,Drinking warm water, Saline gargles Avoiding to speak,not to shout ---are few palliative &helpful measures.
Please advice your sister to follow all these ,after an ENT's advice.& not to jump on Cancer without many other causes for hoarseness ( like Thyroid
problem -which are easily treatable.
With best wishes for early cure & a long healthy life,