I was mixing things up, even though I quoted it. This is what happens when you come from work tired.

I have thought over the course of the episodes that Ryouko or Sayoko were potentially Kuniko's mother. Momoko ruined the possibility that it was Sayoko after saying that Sayoko's daughter is around ten, well too young for her daughter to be Kuniko. Now that's back to Ryouko only.

I've never once entertained thoughts that Karin could be Sayoko's daughter.

Sorry for the confusion. This paragraph was all backwards:
Quote Originally Posted by Ryllharu
I was starting to think so as well. Originally I thought it was Ryouko, but recent events made me believe that anyone coming from the grandma couldn't possibly be that evil to their own daughter. As soon as Momoko mentioned Sayoko had had a child, gears starting whirring in my head and it made so much more sense. Then Monoko ruined it by saying the child must be around 10, and Sayoko confirmed it. Now it's back to assuming it is Ryouko.
I was thinking Kuniko when I wrote it.