@Gambino
She threw him out not out of pure malice. She did it because she wants Ning'er to be the target of Nie Li's affections, which, in her argument, is still stupid. Nie Lie can't simply change his love to someone else. Ironically, so many people seems to hate on Ziyun when she's the one trying to let Ning'er, your apparent favorite win and be happy! Judging by her past life with Nie Li, it's clear that once she's honest about her affections, she's just as loyal and a great partner to Nie Li. It's just that in this life, things turns out different and instead, she puts all her work on becoming a good future city lord, which is a respectable goal, at the expenses of her true desires. So Nie Lie will need to help her overcome this internal conflict where she can be happy with her desires as well as becoming a great lord for her city as part of her duties, and also be on great terms with Ning'er (which she already is on the path for). Of course, this is completely setting up for a harem end.
Either way, I honestly am a bit surprised at all the hate she gets. I agree currently where they stand, she's not agreeable. However, you have to think of why she behaves the way she did and also the situation that leads it to where they are now.
@Kaarme
I agree. She clearly is a good person underneath but circumstances leads her to where she is. If Nie Lie can help her overcome all this and bring out her original personality and her true desires, he will definitely have someone, just like Ning'er, fully have his back at all times. This is also precisely why Nie Lie loves her so much and have so much trusts in her, because he has seen it and experienced it in his previous life.
Honestly, I find it often that in series