the information that you posted is INCORRECT. please know your facts before advising someone on a risk.
At no time were you ever at risk of contracting HIV in a barber shop.
Did the scratch bleed? The only limited risk would have been if her head bled and there was blood on the barber apparatus. But again, very limtied risk. She may be tested 3 weeks after it had happened.
HIV becomes inactive once exposed to the air (once outside of its host). With this in mind you CANNOT get HIV from environmental surfaces, like toilet seats, MANICURE/BARBER EQUIPMENT, shower stalls, drinking glasses, toothbrushes, etc.