It sounds like what your wife is saying is that this is a personal decision. If she is not a minor that is correct but I know what you are saying. You want the best for her. She is not having the lifestyle that supports being healthy. The problem is that your daughter has to want this more than anyone. She has to not accept being overweight. This is a personal decision. She may feel hopeless about her weight and this could cause her to not do anything. Sometimes people do nothing because they feel it is hopeless and it looks like they don't care. I would compromise and find one resource for her. Give it to her and then back off. Anything more than that will be a problem. If she wants to lose weight she will take the resource and act on it. She may just not be tired of this at this time. You can't push so you have to do this gradually. Tell her you care about her and you want her to be healthy. Beyond that you have to let her decide.
If this has been helpful press accept