I'm the oldest of three adult siblings. My youngest sister, “Sue” was diagnosed with chronic depression, bipolar disorder, and within the past year, narcissistic personality disorder. Since the narcissistic diagnosis, she's stopped seeing her psychiatrist and stopped taking her medication.
She's always had issues with pathological lying but I recently found out she has been lying to my other sister and parents about me for years - hurtful, relationship-damaging lies my family believed and she continues to tell to this day. My heart is extremely heavy because I'm contemplating severing ties with her. I know her behavior is largely because of her mental illness but I feel I need to emotionally protect myself from her. I'm at a loss for what to do.