I think Oka is just stupid and naïve. She wants to believe the best in people because she's a teacher. She may have punished Hugo because he was trying to kill the others, but maybe in her mind, stealing his skills was punishment enough, like standing in the hallway with buckets. In a sense, she forgave him for trying to outright murder others, and it was obviously her mistake that led to others being killed, including Shun's father, probably his brother, potentially his other brother, and her elf father.
We still don't really know why she reacted the way she did to Sophia. Did she not expect one of her former students to be on "the bad side"?
I think she's the one who told her father about the reincarnations. But I also think she had good intentions, not knowing the means he would employ to find them.