She's a narcissist. My parents thought they couldn't have kids, so they adopted. She was spoiled rotten and the center of my Dad's world. Then 2 years later, middle sister was born, and two years after that, I was born. I don't think she ever recovered from the shock of no longer being the star.
She was always beautiful and rail- thin, and was always the center of attention. She was Dad's favorite, even though she grew up to be a drug addict and alcoholic. She went through two husbands and her son (that I babysat for years) died from drug use just before his 19th birthday. Since then, she's lived with or been engaged to a few guys but it never lasts
Years later, every time I see her, she comments on my appearance ("they hired you? I thought they'd want someone with Front Office Appearance?"), that my husband of 21 years is not good enough somehow, that her salary in commercial real estate isn't enough for her to get the Mercedes she really wants ("why do drive that beat up old Prius? Aren't you embarrassed?") and just generally puts me down. "You work in a store? Couldn't you find anything better?". Add on to that her "woe-is-me, everyone is so unfair" speeches, and long diatribes
about how tragic it is that she is single at 60.
So... yeah.