Re: How to handle my daughter?
It's interesting that of the two, you tend to have the more understanding nurturing approach. I'm often getting in fights with my wife because she's over nurturing and never holds anyone accountable.
In your case though, I think you're on the right track FWIW. But a blended approach might also work. Giving her time to get her body in order and consider her priorities might be just the thing. On the other hand, there's nothing like working in a low level job with go nowhere co-workers to help re-focus your studies. I know it worked for me.
In any case just bringing her home to a little pampering, health building, etc might help you understand where the real issues are and help her regain her center.
As far as naturopathic approach over medical doctors - we all know AMA medicine is a fraud when it comes to curing disease (mental or otherwise). I'd tell your wife you've tried it her way, why not see if a naturopath might have a different approach that could work. Since it's all natural it can't hurt anything - worse case is it doesn't help any more than the MD's could.
Personally I also swear by SAM-E during those times when I've felt depressed. Even if the reasons were known to me and unavoidable. It still works magic on me (especially the Nature Made brand that you can find everywhere). Good luck!