Does anyone have a loved one with Alzheimer's who also has COPD and is on oxygen?

iIagree that the oxygen issue will be challenging. Have you asked her doctor for suggestions on how to ensure she wears it? Depending on how advanced her Alzheimer's is, maybe you can strike a deal with your mom. She wears the oxygen for one hour and then she gets to go without it for 1/2 hour. Then she wears it for another hour and so on. However, this may not be reasonable depending on her Alzheimer's but if this would work it's better than her not wearing it at all.

As for her inhalers, try giving her an empty inhaler and let her puff on it. There's no medicine inside to harm her or affect her mouth and throat and she may not realize that it's empty. Again, this is depending on how advanced her Alzheimer's is. 

She still needs her maintenance inhalers so I wouldn’t “take her off” these but supervise her daily doses to assure she takes them correctly. Stopping the inhalers will make her breathing more difficult and then the oxygen will become an urgent need.
As far as ways to get her to use the oxygen 24/7 that is an ongoing challenge, especially at night. I would just suggest supervision during the day to assure she gets the benefits at least during awake hours and try your best with the nasal cannula at night by putting a bit of Vaseline where the tubing sits on her nose and placing the cannula tubing to the rear of her head vs the front. This will be an ongoing challenge.