That was sort of the point (abruptly pulling the rug out on a character that looked to be a long term foe for Boyd) according to the writer's recap that they posted yesterday. Unfortunately, they took down the blog from yesterday (
Q&A with Truth and Consequences Writer Ben Cavell) and I don't know if/when they're going to rehost it. I'm probably not explaining as well as I can, but they wanted to ratchet up the tension and the shock value in that scene by making it a surprise that Billy went out so quickly. I'll link the blog if they put it up again and you all can read through it. Obviously intent doesn't equal proper execution and a good reaction from the audience, and a number of people here seem dissatisfied with the way that all shook out. I thought the scene itself worked pretty well, though I'll be disappointed if that's the last we see of Billy as he was a character with some promise.
According to the writers, it was intentionally vague and it's up to your interpretation whether or not she was doing a warm reading in that scene.