I might be wrong but basically what happened is Rubi's brother took her to the mirror room to physically abuse her in private. Freya saw this and thought they were going to have some incest relationship, so she brought company to catch them in the act only to find Rubi in the middle of physical abuse. Instantly the ML jump on Rubi's brother and start wailing on him, this incident shock Freya so much she went to the monastery and become a nun living in seclusion.
@. yep because before this he kiss Rubi on the lips and Izek sister, that knight whose always with the sister and Freya saw them , so that's why Freya told Izek w/c Izek doesn't believe and this happened tay mirror room scene