I've been in EMS for 22 years, and a paramedic for 14. I've never seen a COPD patient lose their respiratory drive due to hyper-oxygenation, and I don't know any other EMS providers who have either. From what I understand, it's mostly a theory, and requires long term exposure to high flow (longer than we have with the patient).
That doesn't mean I think we should throw oxygen at everyone just because we can. Quite the opposite. I think we need to be judicious. This is a case where you need to go on clinical assessment. How was her color? Was she diaphoretic? How was her capillary refill? How were her lung sounds? Could she have been in pulmonary edema? Anytime I see a patient who needs dialysis that is short of breath, I am diligent for assessing for pulmonary edema secondary to fluid overload.
Remember also that COPD patients generally don't have a problem oxygenating, they have a problem ventilating, while CHF/pulmonary edema patients are the opposite.
Another thing to remember is that if the patient's CO2 becomes too high, they may become sedated and their respiratory drive may suffer, requiring assistance. Again, problem of ventilation, not oxygenation.
In the end, you used the tools you had available to you. I'm not sure you needed that much oxygen (I wasn't there) but I also don't think you did a lot of harm.