Hermione was taking a gamble being so honest. Especially with a man that had already proven that he would report back what she said to his superior officer like a good little soldier. She knew that Draco would pass along the contents of their conversation, inform Rodolphus that Antonin didn't want to stand in his way to power. Maybe she would come to regret being so open, but she couldn't afford to consider that yet. War wasn't just fought on the battlefield. It was also fought in private conversations between those on opposing sides.