Difficulty with decision making and abstract thinking, along with lapses in memory and personality, are possible early signs of Alzheimer's disease. Additionally, erratic and poor choices by someone with these symptoms are particularly worrisome signs. A physician should be consulted for assessments and diagnosis.
The earliest change you may notice with your mom in relation to her decision-making, and one that might be an indication she is developing the disease, would most likely be the way she handles her money and finances. People with Alzheimer's have difficulty with abstract thinking, thus working with numbers and money matters becomes more challenging. For instance, if she is normally conservative and cautious about her spending or sticks strictly to a budget, you might see her giving donations to various unfamiliar causes, to telemarketers who call her or writing checks unwittingly to convincing solicitors. She might even miss paying monthly bills. Another change you might see is her lack of understanding on the concept of numbers and what they represent.
Do the lapses in judgment your mom is having include such things as handling household appliances improperly, wearing mismatched clothing, wandering or even no longer being able to distinguish what is safe for her? These also might be indicators of dementia or Alzheimer's disease.
Other signs of Alzheimer's disease in addition to poor judgment include short-term memory loss, time and space orientation, personality changes, difficulty with communicating and comprehension, difficulty completing familiar tasks and social withdrawal.
Keep in mind, however, that other conditions can cause impairment or lapses in judgment, such as depression, alcoholism or bipolar disorder. It is best to consult a physician to gain a greater understanding of your mom's symptoms to ascertain a definite diagnosis.