Why do you think your sister is like this? Does she get along with your mom? Did they have a falling out or is your sister resentful of something from childhood? Just wondering because it sounds odd that your sister is so different from you. I wonder if there was something different in her upbringing or if your mom treated her differently?
Even in the same family, personalities and life experiences differ. My brother was older and looking back was enabled by my parents
He never had to work for anything because it was given to him. People like this always have a safety net but do not see how it impacts others. To me it's in the mental health regime. Possible depression fear of success, narcissism as noted. We are like night and day. Often alcohol abuse, drugs have had an impact.