Are you a foundation expert? Are you a concrete contractor? NO... hell no. You state,"If one only one side, that means that that side is failing due to improper foundation construction." You don't have the proper information to make this statement. Did you visit the site and visually examine the pour? No. Are you a structural engineer? No. Have you ever heard of surface cracking related to not keeping the surface moist during curing. I doubt it. These surface cracks are NOT fault lines. They are NOT an impending structural failure of the slab. They are the result of not keeping the concrete moist and working the surface properly after it sets up. This situation is MOST likely what is happening. Stick with something you know something about. Don't try to be a "know-it-all". If she is that concerned she should have a STRUCTURAL engineer take a look at it. P.S. To show your lack of foundation knowledge you DON"T put in rebar with a post-tension cable system. "Cable Lock" is a system used in FOUNDATION REPAIR.