Yes - clearing the codes also turns off the dash light.

If the cause is still there, the light will come on again - often after a few minutes drive.

Our most unexpected cause of a Check-Engine light was a tranny fluid leak that got on the exhaust system. Oxygen sensor,located at the cat converter, was soaked in fluid and failed due to that.

Have her take a look at the plumbing there, look for oily goop on the piping. It's beneath the front passenger seating area. If still fresh from being driven the outside of the pipe might be smoking from burnoff. Oxy sensor screws in from the other side so you don't see that without getting under the car, but all she really needs to look for is the goo on outside of piping, and smoking if recently driven and warmed up.
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Sven: '89 245, IPD sways, electric rad. fan conversion, 28+ mpg - auto tranny. 850 mi/week commute. '89 245 #2 (wifemobile). '90 244 (spare, runs).