That was hard to read. But we just witness why Sara is needed. Natalia was wasting away, not sleeping and barely eating. And all her people were saying is that sylph children sure are impressive. Yes, so impressive they died on you and you didn't even wonder why... Take the sword by killing Sara would've save the people for now. The next battle Natalia would've died before their very eyes and they would be in the same situation. Heck, with how she was Natalia couldn't even produce an heir.
This way, Natalia is forced to take care of herself because the sword won't always be available (you know, fight to literally see another day) and Sara... Well, I guess she's already paying for being in the wrong place at the wrong time. I would share my chill pills but I'm on prescription... I'm just given what I need, not enough to do away with my life 😐 (that sounded less gloom and doom in my mind)