You can also use hotglue to seal off the rusting area. Just cover it completely with a layer of hot glue (works the same as aquarium sealant), let it cool and harden, and at least the rusting problem will be solved. The fraying problem, that could be a bit harder. If you have pinking shears (those scissors that cut in a zig-zag pattern) then you could try shearing the edges, that should prevent the majority of the fraying. Pinking shears are used in sewing to prevent fraying, so I would assume it would work on the fabric plants as well.
I hope that helps for anyone who has these plants and really wants to keep them. :)