Thank you for the response, Ruari. I believe you are right.
Her behavior pushes people away. The situation has gotten to the point where no one in the family can even hear her name without groaning afterward. I'm the type of person who needs active, constructive communication in order to maintain a relationship, though, so I'm thinking I'm going to have to love her from a distance from now on. But then I end up feeling guilty for not visiting with her. x_x The cycle of guilt and frustration in this situation is endless, it seems.