Hi crayonmum,
Do you hv the mummy's user ID? This is really bad. Do you know you can report her link in the WTB thread to the moderator? It is wrong and against the SMH regulations to sell in the WTB, Free Items and discussion threads. So mummies, if you happen to see any of these threads, you can email these links to the moderator for their necessary action. It'll be a big help to the moderators.
Thanks for sharing, it's good that you share with us so that we will stay away from her. I agree with you, I don't think it's right to sell an item that you just bought from another person, even though that item does not belong to the seller anymore. The seller may not feel good seeing the buyer selling her item. I would not feel good if I see my item is being sold by the buyer.