Yup. The scars of cheating never usually fade. If a partner cheats once, the looming suspicion and thought of them cheating again never leaves, even if they want to forgive and forget.
Whether she checks his phone in the middle of the night, or he comes home even just a bit late, or even if one small detail is different from his stories, she'll always keep wondering if he cheated on her again. So sad.
If he truly did sleep with the purple haired girl, I'd honestly just want them to break up. It's absolute torture to stay, even if they love each other.