Did you notice how mom says she understands whats going on?
I'm positive she was npt refering to their "friendship", that whole scene I was scared that Ayaka was going to throw Sora out of the closet and I was glad she didn't but I guess mom got it anyway
The question that remains is if she let go to let her daughter sort her feelings out or just because everything was becoming more difficult than she planned and she could not be arsed to care more than she did