Hi,
sorry if I appear to be hijacking your thread but if I remember rightly at the time she sold you the Mini it was still with the cherrished plate. She then transferred it to her new car? That has to be done by DVLA. I think this can take up to a couple of weeks or so to complete, during which time you parked in McDonalds with the plate still on the Mini. She can draft a letter to them stating the date she sold the car and that any further information they require they should contact DVLA. It appears the time scale from when the offence took place to them obtaining details of the owner in relation to the offence overlapped the transfer if you understand what I mean? On the V5 ( log book ) it will show the date the vehicle (your mini) was sold to you. Your friends does not have to disclose who she sold it to as it is not deemed as a traffic offence under the Road Traffic Act. Also it would be a breach of her human rights under Article 6 of the European court of Human Rights to disclose who she sold it to as again no Traffic offence has been committed so they have no lawful right to that information. Let them do the work, not you or her

Did the letter she received state it was a FINE? or penalty charge, in light of it being FINE, no one has the right to issue a fine apart from a court of law. So says the law!
Hope this helps, a bit long winded but when I get on my high horse lol