A/C light

It could very well mean that something is amiss with your AC, something that is causing it not to work. Perhaps it is the belt, perhaps it is something more insidious. I believe that it should be automatically coming on with the Defrost setting to dry out the air. Try using the AC only and see if that causes the light to come on. See if it makes cold air come out (I would do this when the car is all warmed up inside and try it using 'inside air' to see if it chills that air). If the AC works fine it might only be that the light bulb is burned out or it is not telling the AC to turn on anymore for some reason.

Come tell us what this test reveals. Tomes

Or, it could mean her car is not supposed to have the AC come on automatically with the defroster. Mine does. My son's 96 Camry does not. I'd suggest looking at the owner's manual, even if it looks scary, and requires going outside to get it.

It's normal. The defrost mode uses the a/c compressor. Most newer vehicles design their systems to operate similarly. Your MPG will be reduced as well when driving in "defrost" mode due to the extra energy required to run the a/c compressor. I drive an '05 Corolla LE and it works just like yours.

OBTW ronbon, if you have the recirculate button pushed in and you select the defrost mode, it will cancel the button out. Normal.