In 4.18 The Monster At The End Of This Book, how can Lillith escape if she's standing almost directly on a Devil's Trap?

In the hotel room, she uncovers the rug and sees that Sam has drawn a Devil's Trap. But when Chuck comes in and she gets up off the bed, when the demon leaves it's host, I swear she's standing on the rug....and the Trap looked quite big...? :S