My husband was in rehab for 3 months a little over a year ago. I was very concerned about how my actions and words might impact him, but I really think I was off base in worrying about. How well your wife does in rehab has very little to do with you, assuming you aren't mean spirited. It is her journey.
When my husband went to rehab I made him 4 promises: I would drive him there, I would pick him up, I would pay for it, and I would look after his 90 year old mother while he was there.