As I understand it, the dna is usually sourced when the hair root is intact as that contains skin cells. Hair itself is keratin and can be type matched - eg coarseness, colour, texture, tested for chemicals (eg environmental, dyes, medication, recreational) which all amount to circumstantial evidence but to get a DNA match actual cells would be required. Assuming the donation is the result of a haircut and not epilation or scalping - she’s probably in the clear.