All the information she needs is here:
http://www.clsdirect.org.uk/legalhelp/leaflet3 1.jsp?lang=en
It can be done simply by useage, but although legal it can be difficult in respect of official documents.
But don't forget that changing names on passport, driving licence and so on will probably incur a cost.
Insurance companies, banks, council, gp, utilities and so on will all have to be informed.
For the sake of simplicity it will probably be best to pay a solicitor the �30 or so fee. Or there is an online service that does it for under �10.