I adore Amy and Duffy equally. As different as they are from each other in just about every way, they both are highly talented artists that deserve respect and support.
The only non-original song on Rockferry (deluxe version) is Please Stay by Burt Bacharach. She redid the McCartney Bond theme Live and Let Die for a charity record and the Lorraine Ellison classic Stay With Me for the film soundtrack The Boat that Rocked. She hasn't recorded any other covers although a couple of tracks like Oh Boy and Enough Love were written as demos for Duffy by Richard Parfitt back in 2004