Given that I could easily see the twist going in three different directions, I don't think I'd have confidence guessing what someone else's prediction is. Without giving away the ending, I anticipated that the ribbon was symbolically/factually "binding" something. But I saw three possibilities:
1. It was binding her obedience; removal would result in her (either voluntarily or involuntarily) destroying her husband, or perhaps simply would allow her to leave him (as with the fairy wife of Myddfai, or as with the return of a selkie's skin).
2. It was binding her physical form; removing it would result in her changing (voluntarily or involuntarily) into a non-human form, possibly with other consequences.
3. It was binding her body together in an intact form; removing it would cause her to literally fall apart.
These merge into each other at the edges, so grouping them into three and only three possibilities is somewhat arbitrary.
no subject
1. It was binding her obedience; removal would result in her (either voluntarily or involuntarily) destroying her husband, or perhaps simply would allow her to leave him (as with the fairy wife of Myddfai, or as with the return of a selkie's skin).
2. It was binding her physical form; removing it would result in her changing (voluntarily or involuntarily) into a non-human form, possibly with other consequences.
3. It was binding her body together in an intact form; removing it would cause her to literally fall apart.
These merge into each other at the edges, so grouping them into three and only three possibilities is somewhat arbitrary.