Danielle has infiltrated the losties just as Ethan and Goodwin. For some reason they trust her, even though she stole Aaron. She is a plant, the others lie, and she used the trust the losties have in her to get Ben into their camp. Ben was not captured by Danielle. It was a obvious setup to get him inside the camp. If she actually did capture the leader of the others, regardless of where he was held they would have come and got him back. They can come and get anyone they want anytime they need.