I don't know what your mother told AA, but if she specifically stated that she suffers from COPD and requires an inhaler, AA's reaction is no different than most carriers will (or at least ought to be). There is no policy per se relating to COPD, simply a policy that AA reviews medical concerns with its outside contractor medical desk and that may result in a requirement that the passenger document her fitness to fly.

AA has no way of knowing the severity of your mother's condition and therefore will not just accept a passenger's statement that they are fine.

Presuming that your mother has discussed flying with her treating physician and that he has approved air travel, there is no reason to provide details to AA. Wheelchairs can be ordered as late as the departure gate (in fact, on arrival - but there will be a wait) and all she needs to disclose is that she needs assistance over distances.