It's a real good point, but Satoko never had to live through what Rika did. She only saw the same things Rika saw, and instead of feeling sorry for Rika or even ponder on why it is she had the beliefs she did, she decided Rika had to pay for even daring to think about leaving her behind and the best way to do it was to break her because... reasons.
Witch influence or not, what kind of person sees their best friend suffer and decides to continue that same suffering to "teach them a lesson"? Where was it even stated in any of the chapters that Satoko would've ever considered abandoning or throwing away friendship just like that?
Obviously you won't find anything because Satoko had never gone through such a situation in the original.
We happen to meet Rika when she's already at the end of her journey, but if we spent eight VNs with the original Rika before Hanyuu fucked everything up, we'd probably find her change into a smug, borderline sociopathic alcoholic pretty jarring too.
The tragedies aren't even the most significant aspect to consider, it's the very nature of looping and the endless repetition that would lead anyone to eventually develop a radically different mindset from the rest of humanity. Rika also had someone encourage her to try to continue thinking like a human, with Satoko serving as the strongest link to her own humanity, while Satoko's guide just encouraged her to go wild, so it was only to be expected that Satoko would get so much worse so much more quickly.
Obviously, they could've done a much better job depicting Satoko's fall by doing it in a much more gradual manner, especially given the implication given by the last episode that Satoko spent much, much more time looping before she started her game than what was made apparent during Gou, but I don't think that the fundamental idea would be impossible.
There's also the betrayal aspect to consider in Satoko's case. Finding out that the person you trust the most was actually lying to you all your life kinda tends to do a number on people. It gets much easier to do terrible things to someone when you realize they're kind of a bastard, anyway.
They certainly could've spent more time exploring the whole situation, that's for sure, but since they only had 39 episodes available to them, they
obviously had to cut some unimportant aspects like say, why Rika and Satoko are so dependent on one another, why Rika's dream changed from wanting to live peacefully with her friends in Hinamizawa to her wanting to go to St. Lucia, or the various traumas both characters carry with them and how they inevitably led to disaster.
These are all issues that could easily be solved if the plot actually spent a little time exploring and explaining them, and the manga already did a much better job using only a couple panels, but Passione just had the shittiest priorities imaginable.
There's all kinds of possibilities to explore in the Satoko/Rika dynamic, and they completely failed to use any of them and instead just kept going on and on about the studying, as if that was the only thing going on between them.
I really shouldn't have to go to the fucking gacha to find writers willing to explore topics that can be traced all the way back to the original VN.
