What do you mean by "ruined"? Did you give it a nasty scratch and it won't play? Try using a DVD scratch remover or plastic polish. It could restore it back to working condition and you might be able to get by with an apology for the scratch that doesn't seem to affect play back. Of course, any damage beyond that and yeah... best off just buying a used set and extracting the disk. Or... buy a new set and give that to your mother, keeping her used set.