@KazutoKatsuragi Your point 1 doesn't actually answer the issue. If Iglis hurts or murders or makes the guy disappear, it will cause a diplomatic incident. This is a guy that can murder a noble in the middle of a party, then tell the authorities "Say that he died of natural causes", and they agree because they don't want to sour their relationship to the Highland. It's not a problem that you can solve by punching. So after she beats the guy up, does she have a plan for dealing with the fallout? She is perfectly aware of Rahal's influence, and she was a king so she can't ignore the political outcomes of her actions.
Your answer to 2 Is the same. If Eris succeeded in preventing Iglis from going, it would just make Rahal angry for being kept waiting. He might murder someone else for the insult, then still demand that they send someone over for him to rape, or return to the Highland and say he was mistreated and end up causing a diplomatic incident again. So if she wasn't planning to take her place, what was she planning to do?
As for 3, I didn't understood why he wanted to kidnap her. I mean, he is a rebel, but how would Eris fit into her plan. It seemed they had been travelling together, so why choose that moment, when there was a witness he didn't seem willing to eliminate?
So yes, I understand the immediate thing they're doing, I don't understand how they relate to the broader situation they are in, and how their current actions improve the overall situation, instead of make it worse.