Please tell me that Kagami's mother is not sabotaging their relationship because she is jealous and is actually planning for Indou to be the replacement for her mother. That would be a bit much.
I mean, it's a possibility, but I suspect it's rather that she thinks it's better to separate them now than to have them go through the same that she did with Indou's mom. Not the brightest idea anyone has ever had, but understandable to an extent.