If she felt threatened again or she was concerned Oliver would be put in danger, she would tell Antonin everything. He might hate her again, but at least he would understand the severity of the threat. Draco was unreliable. She didn't know his true feelings or his true alliances. It was very likely that he'd been manipulating her from the start. Certainly she used to feel fuzzy-headed around him, like she wasn't even in complete charge of her own actions. Perhaps more about her changed with the removal of all of the memory charms than she thought.