Clearly, the tag is just a prop.
Her story is that the necklace "may have been a sample" and was given to her a couple of years ago by a friend who "works for the company." (Uh, which company?)
It's an interesting legal question. Can someone take an authentic Coach scarf, cut it up, and use it to make something else? I think it's called "repurposing" or "upcycling."

What about artistic license? Didn't Andy Warhol appropriate the Campbell Soup can for his famous paintings?
"Andy Warhol was notorious for his paintings of Campbell’s Soup cans, and was sued by Campbell Soup Company for copyright infringement. But Warhol and his works became so popular that the corporation later decided his paintings were actually good, free, advertising, so they let him continue his use."
http://artbistro.monster.com/benefits/articles/11435-copyright-trademark-protection-must-knows
Anyway, it seems to me she can't really
prove the necklace is an authentic Coach product, made and sold by Coach. Can she still sell it as "designer inspired" merchandise? What about claiming it's a "sample"?