She waits until they're out of town enough that she thinks that she's safe to tell him. She doesn't really want to, but he deserves it, doesn't he? Besides, it's not like she's going to get away with lying about it forever. "Because I'm protecting you," is what she says firmly.

They still have a ways to go before she'll tell him exactly what she heard, but she can let him know that she hadn't been doing it to hurt him.