The way to confirm that you are right about the rate is via the Works Rights Helpline on the 0800 number above.
The way to seek redress is also through the same phone line, but you can also do it here via this online form.
https://payandworkrig...ct.gov.uk/complaints/
I would be wary - whilst she would very likely win the claim, she needs to think about what would happen if the employing hairdresser decided not to continue with the apprenticeship when it finds out it has to fund it at £95 per week.
Maybe the Helpline can advise whether a retrospective claim after the end of the apprenticeship is possible.