I, for one, loved every part of it. I think the mom plot's fine. It's a little direct to serve a very specific purpose, but I think that's okay. I mean, it's like when the heroes spend the whole story trying to stop the big bad from getting the macguffin, then the big bad gets the macguffin, and it results in a big epic fight scene against impossible odds that we all know that outcome to but is fun to watch. The confession in the airport was that scene. As a writer, I know that "realism" isn't really what you should be going for. Gotta make that drama happen ;o
Maybe I'm just giving the author the benefit of the doubt, but I thought it was an amazing story with a great payoff. I cried at the end. Seeing how happy everyone was to have Sora back, and the scene with Sora and Ayaka in Sora's room, just gave me such good feelings. Plus, as a person with an abusive mother (though maybe not as bad), those interactions made perfect sense to me. Abusers have a certain level of perceived control over their victims. She wasn't throwing in the towel, she was letting the leash go taut, convinced that Sora will come running back to her.