I am at a loss...how does a person with a personality disorder manipulate people into being their friend?

My mother has a personality disorder, she abused her husband (my father), her children with emotional abuse, manipulation, telling lies about our father, yet she has managed to make loyal friends with good people who support her as she journeys thru Alzheimer's. These people are willing and able to help me out by calling me when they are concerned about my mom. They know she has Alzheimer's and compassion for her overwhelms me because of how horrible she has been during my childhood and adulthood. How can a person with a personality disorder develop these relationships with healthy minded people who support her?