Chemical straightener has Ruined my nieces hair HELP!!!?

my neiece has naturally curly hair and went for a hair relaxer but instead of smooth sleek straight hair..her hair is still curly and its very dry..very dull and by the looks of it very broken esp around her hairline..ive been a hairdresser and never encountered anyone who had a chemical relaxer so i dont know what i can do with it..my neice is 14 years old and the age where hair is important to a young girl.....so any tips of improving her hair and give it some sort of sleek shine without shaving it all off?