What is the cause of low hemoglobin count of 8.2 in a 72 year old woman with no history of blood problems ever?

Could be many things. She should be evaluated by her doctor as soon as possible for further evaluation. There are a lot of things that can cause significant anemia- from just being malnourished, bleeding, other chronic conditions/inflammation, malignancy etc. Bring her to see a doctor.
Several. There are many causes of anemia: this needs to be evaluated by a health care professional. History, physical examination and blood testing will be required to make a diagnosis.
Anemia . Anemia at this age needs to be worked up. Most common issues are related to blood loss in gastrointestinal tract, kidney disease, nutritional issues, alcohol abuse, gynecological disease, and many others. She should be evaluated by her regular doctor asap.