The Aosawa Murders question

Hi! I just finished this last night. I think I understand everything, except for perhaps what exactly happened in the blue room. From what I understood, Hisako had a Nietzsche like complex and wanted her family dead, so she convinced the mentally unstable man to poison them and then commit suicide. She enlisted the kids from the church a couple of times, first, to call the house the day of the murder and years after, to burn the bookstore in order to destroy the only evidence against her (the slip of paper with the address). The author was obsessed with her and wrote the book as a means of trying to let her know.

I am super confused as to what happened in the blue room with the flower. Was her mother abusing Hisako and was that her primary motive?

I think Hisako was getting abused by his mother in the blue room. She wanted to escape but couldn't so she cleverly used the unstable man to poison the whole family, whom I think, turned a blind eye to the abuse. Just what I thought.