Honestly I never thought of it that way.
I mean, she definitely became the majority of what drove and motivated Adalind from mid-season 3 to the end of the show, and I have issues with basically all tropes hovering in that area of “motherhood as motivator.” Shows (and action movies) love to do this to women: give them a kid to motivate them or further/change the course of their development. Because apparently nothing else works for us ladies, right?
I kind of see Grimm as all one long-game plot, though, of which Diana is only one part. Granted, in some ways it’s not a very well-executed one. I feel like they stretched it out way too much in the name of mystery, and then had to squeeze everything in those last two seasons when their ratings dropped…to the point that an endgame which really started with the very first episode ended up feeling less tied together than it could have in the end.
I mean, think about it: Nick, one of the last remaining Grimms, gets that first key in the pilot, one of seven created and scattered by the Knights Templar, who were apparently supposed to be Grimms. And then he continues to gather keys throughout the seasons, until he has enough to get a partial map.
Those keys lead to the Black Forest and the Stick of Destiny, which turns out to be a piece of the magic staff that Zerstorer holds, and which Nick eventually becomes the protector of after defeating Zerstorer. Meanwhile Zerstorer’s goal was to control Diana, who only existed via Adalind’s personal plotline, which was set in motion back in season one when Nick took her powers…or, arguably, in the pilot itself, when Renard sent Adalind to kill Marie as part of his ploy to get the key.
So many little things could not have happened without so many other little things happening, to the point that when you step back and look at it, it looks much tighter story-wise than it seems in the show. There’s definitely an element of destiny running throughout it, like everything that happened was meant to happen in one way or another. Unfortunately, we don’t really get the full impact of that in the execution.
So…I guess the idea of Diana being a plot device never bothered me because that’s not how I saw it, so much as that she was clearly a key player in whatever events were going to unfold, for better or worse.
That being said, I still have a lot of questions. Like how did Zerstorer end up in the other world anyway? Did he originate there? If so, how did he get the staff? Did it originate there or in our world? Did he once cross to our world and have to be banished? Did he originate here and have to be banished? Can I please get a comic series telling me the story behind those damn knights and the damn stick and Zerstorer and how it all ties together, PRETTY PLEASE?