I love how you say he hasn't given her a reason to hate him when we know f*ck all about what happened between them because no one is spilling the tea. He could have cheated, sure, but there are things other than cheating that could also be super hurtful and depending on the person be grounds for a permanent break. Like, he could have told her she's a waste of space or that he can't stand being with her because of x,y,z. I don't know, there are so many things that would be super hurtful to someone like Niomi, who bases so much of her worth on what others think of hers.
And even if the worst thing he ever did was break up with her, he made her picture perfect life publicly crumble. I doubt Niomi would forgive that easily.