Here's a thought: I think Isabelle retained her memories like Kaoru and was given the same warning not to practice magic until 3yrs old but she didn't listen. Hence the consequences she develop an illness. Because her skills had something to do with "transferring/switching" she took advantage and used it on Lila. Also because she figured that it's free sailing being a saint, as someone said earlier she used the ring to distort the truth about Kaoru's title.
I’ll be glad when he finally gets them one by one and bring their family to ruin. I mean taking that type of bullying that far, I think he’s justified in making them suffer. If anything I hope he disfigured them as well as traumatized them for life because killing them is too easy and too humane for the despicable vermin they really are. Looking forward to their demised when they can’t stand living in their situation.