Thanks, LasMa for sharing your insightful idea obtained through experiences.
Thanks, mcat, and you’re right, my words do come from experience, and from doing it wrong for a while. 
When our D was about 21, things were going badly enough that we had a family meeting where the three of us sat down and defined what our relationship was going to be going forward. The bottom line was that we agreed to get out of her business. It’s been much better ever since then.
I wonder whether you have any wisdom about how to not be a bad inlaw.>>>>>>>>>
Stay out of their business.
If they ask for an opinion or advice, tread lightly.