Paying back bank over draft after 10 years in the uk?

I wonder if anyone can give me some advice,i am posting this for a friend of mine who is 75 years old..she had an overdraft at a bank of �300 well over 10 years ago and now another company has bought this debt and demanding over �1700 fro her,do these debts ever get righten of after so many years as been reading on the internet and some sites say NO some say after 6 or 7years,she is willing to pay back at a weekly rate but only a small payment as shes on a pension any hel ..please and thank you