Avi issue/dvd player

Hello,

I sent a friend some avi files on a dvd disc. They play fine on her regular dvd player. However when she tries to make another copy of the copy I sent to her they copy fine, but will not play on the dvd player.

I know that the type of codec matters as to how the avi files are encoded but I’m not sure what could be causing this. Is another codec involved when she just copies my avi’s to her own dvd disc?

Thanks so much!
Nancy