What clues indicate that she knew she would be taken?

Minerva refuses to go up to the loft, instead insisting on sleeping in the middle of the barn floor. At night the group understands why. The Recruiters pull up in their vans and Minerva is able to quickly smile and signal to the group to stay quiet before the agents take her away. In the morning the group realizes that Minerva hid the ladder in the middle of the night because she knew the Recruiters were coming.