We've actually toyed with having a version without the coach that's quite a bit cheaper (~9/month) - is that something you'd find more compelling?
I could see her trialling a comprehensive ($30 a week) package for a few weeks, then dropping to a less intensive (~$10 a week) package that kept her on the right track.
I personally don't think she would pay $30 a week unless the service gave her a significant material difference in lifestyle (which I certainly imagine it could have the potential to do).
i.e., it would help you with churn a bit, I think.