MRCP2-3730

A 78-year-old woman was diagnosed with breast cancer six years ago. She has received various hormonal treatments, but her tumor markers have started to increase again. Her oncologist has recommended a change in her hormonal therapy, but she has refused, opting to let nature take its course. Her son disagrees with her decision and wants her to receive the new treatment. He has questioned her mental capacity and ability to provide informed consent.

As per the Mental Capacity Act 2005, what would indicate that she lacks the capacity to make this decision?