To clarify, this doesn't redeem the princess in any way shape or form, she was just given a push further down her already despicable obsession. Basically, this is just a plot point introduced to make the Saintess guilty, but all she did was accelerating the princess' own degeneracy.
Now, would the princess have gone as far as she did without the Saintess' intervention? We don't really know, but it hardly matters because we know she was rotten anyways. They're both gonna pay for what they've done with interest though. Looking forward to it.