If her name has changed this may not work but you should try a site like www.tracesmart.co.uk
You can search for free I think and then either pay a one off charge to look up the results for one person or pay for multiple results. It's done via the electoral role register so anyone who's registered to vote can be found there. It will give you their address and sometimes also telephone number but this isn't always accurate if they've moved and not updayed their address.
Steve Wright's Sunday show on Radio 2 often puts out requests to find people sometimes for a romantic reason, sometimes the person just wants to know what happened to someone they knew years ago and lost touch with.