Like how leaving wasn't always an option. She'd pledged her life to Lord Voldemort's eternal service. He gave her the order to marry Antonin. Going against her master's orders was a death sentence. Admitting that she couldn't stay married to the wizard because he was physically violent with her when he lost his temper wasn't a good enough reason. It showed her to be weak. Any hint of weakness could be sniffed out by the more ambitious and power-hungry Death Eaters. She would instantly become a target. All of the hard work and degradation since she was pulled from her broom cupboard would be for nothing. It was better that she endure Antonin's tempers with as much stoicism as possible and use his repentant moods that followed to her advantage.