As I say in my previous comment, "antique" is what I thought they had in mind. Anyway, I forced a refresh of "antigo" and asked for "She sells an antque hat" to be accepted. Interestingly, my vocab list includes "antigos" translated as "antique" but that word doesn't appear to have any associated questions.
In English, articles of clothing aren't called "antique." They are "old" or "vintage." Likewise, while ancient clothing exists (archaeologists might find it on digs and put it in museums, or religious people visit it in reliquaries), "ancient" is, 99% of the time, a highly unusual adjective for "clothing," especially any clothing apt to be bought or sold. Hence "old" and "vintage" as the best translations here.