You said she decided to change her name
did she do this legally or just change it. You have to either get married, change it by deedpoll have to change everything the banks passports. Only if she followed the correct route would they chaI am sure you can't really just say from now I Think about it I could use any name run up a bill and then change my name again and start saying I had never heard of anyone called Mrs Blah..
http://www.lawontheweb.co.uk/basics/changeofname.htm