Basically; if she believes the PPI was mis-sold she needs to write to Barclays stating the reasons why she considers it was mis-sold, asking for the return of the premiums plus interest. If after Eight weeks they fail to resolve the problem you are then entitled to ask the financial ombudsman at the FOS (below) to become involved by lodging a complaint.
If you place these words, "mis sold ppi" into Google, you will see sites and forums that explain in great detail what constitutes mis-sold.... along with the procedure and necessary template letters to undertake this process.
http://www.financial-ombudsman.org.uk/consumer/complaints.htm
gcossie - In response they said it would take 6 to 12 weeks and she would have to pay a fee of £10!The above refers to a SAR (subject access request), this is not always necessary for the purposes of requesting a return of mis-sold PPI premiums. ...they could have been wasting your time, effort and money.
All a SAR does is compel them to provide all the documents they hold relating to the subject in question.