Because she didn't care, she pretended not to see him with other women, because she didn't care, she ignored that other women answered his calls. Because she didn't care, she could casually say "I believe you" and dismiss him.
He had anticipated this response, but he still felt dissatisfied. There's a saying about not turning back until hitting the south wall, yet he, on Chuxia, had hit his head till it bled but still hadn't learned to turn back.
Che gave a cold laugh, but it wasn't clear whether he was laughing at Chuxia or at himself.
When Chuxia said that, there was a moment of silence from Che, and her heart reflexively tightened. However, Che didn't say anything but just gave a cold laugh, leaving Chuxia's heart hanging in her throat.
She couldn't see through Che's other emotions, but she clearly understood the signs of his anger. Panic and regret flashed quickly in Chuxia's eyes. Just as the atmosphere had eased slightly, it was shattered by her words.