Actually, D probably wanted to see Gyurie struggle with what to do but ultimately do something anyway. Least interesting option for D would be for someone to be passive. Putting it another way, you could say that D's action was to cause tension... not to protect Potimas. For example, in the WN, D specificaly asked/told Shiro to hep Ariel. Why might she do that? Because she probably approved of Ariel deciding to take action and what that would involve. It's worth remembering in the specific scene where Gyurie talked to Sariel that D forced the conversation to end early. If the conversation had continued it's possible that Sariel could have added a caveat. Still, overall I agree that Sariel is inflexible and while she's trying to do "good" overall, that inflexibility is a problem. It's an interesting dilemma for sure. If we put aside the question of which option is better and whether there's any better options, you could simply say that Gyurie and Dustin have had a long long time to sort things out but failed so why should they get another chance? I'm not saying that this makes Shiro's solution "right" but it at least makes me less likely to trust Gyurie/Dustin's solutions on faith. It would be interesting to see if Sariel gets any further character development. From the limited hints we've gotten it doesn't seem like she has fundamentally changed her opinion but would she do anything differently now? Assuming that she gets rescued in the end, how will she react? But yes, it's interesting that the most powerful character on the planet (Sariel) is also the most emotionally stunted. Should we praise her for developing emotions in the first place or criticise her for not developing further?