I'm sorry your wife is not supportive of the therapy for your daughter. My son has been in therapy for almost a year for anxiety and my husband is not terribly supportive either, although he never says he doesn't want him to go, he's not thrilled about it. Plus our insurance pays for most of it so it's not a money issue.

Your daughter having a slice of cake is certainly not a sign that it's not working! I'm assuming that her therapy is helping her understand why she is overeating and dealing with the issues behind the overeating, which generally has nothing to do with the eating. She's going to eat things for the rest of her life and learning to manage that now will help her so much in the future. How does your daughter feel? Does she think that she is benefiting from it?

Willpower and motivation have nothing to do with it. I'm sure your daughter is motivated and wants to do well at this. Kids do well if they can. So if they're not doing well, then it's our job as parents to figure out what is holding them back, and give them the tools they need to be successful.