This is an allusion because when she wants to sell her hair you know she is going to buy something for his watch. The story foreshadows that while she is doing that, Jim is selling his watch to get something for her hair. Because of this, the story alludes to what is going to happen next.
When Jim “looked around the room curiously” it was a huge hint that he did not like it, but not because of the hair itself because he bought something for it.