I feel like you're jumping to conclusions on this. First of all, if you knew Aiwei, a person with a huge and precise radar sense was in your city, what would you do? I'd offer them a fucking job with either me or the police force. On top of that, we have no idea what their relationship is like and what she did with that information. It's not like Aiwei told her every single thing, either. Hell, as far as we know, Aiwei went to her. He was a part of the Red Lotus, and they don't like world leaders, so it's entirely possible he was putting himself into position to take her out. We also don't know what Zaofu's justice/disciplinary system is like.
As for her relationship with Opal, she wanted Opal to stay because she was over-protective. She admitted that. As for Kuvira, she kicked Kuvira out because Kuvira was going to, once again, enforce a policy that she does not believe in nor support. Why would she be okay with her entire police force, a majority of her financial providers, and two of her biggest city engineers. One of those engineers is also her son, so now her adopted daughter and her son are going to enforce a policy that she is directly opposed to. Besides, Kuvira was never forced to do anything. She made her own decisions and took them to an extreme. Su Yin can't be held responsible for that.