Dav....while not a complete solution, there is a way to deactivate the stop/start in a 2018 Malibu. It requires you to do this every time you start the car. Tell her to shift into L instead of D and press the + button on the shifter 8 or more times to place the range of the transmission to be from gear 1 to gear 9 (if she has the lower level Malibu with the six speed then L6). In the Driver Information Center, on the dashboard, the transmission gear indicator will show "L9" (or L6 if the 6 speed). Your range of gears will be the full range available in D, and the transmission will shift in L9 (L6) mode in the same way as it does in D mode, but the auto stop/start will be disabled. On the highway, the engine rpm and overall behavior is the same in both modes.