It sounds like your sister views you as her competition instead of her friend. It sounds like this has been going on for a while. I am curious to know what your parents think of this. I’m sure they would not be okay with her treating you this way, but at this point in your life you are an adult, and you have say over what a person can and cannot do to you.
The first thing you need to do is to stop giving your sister so much power. Her behavior towards you should not reflect how you feel about yourself.

I think you need to tell your sister that all the non-constructive criticism you receive from her is unacceptable, and you will not tolerate it from this point on. You should call her out as soon as she does it, because if you wait, she might pretend she does not remember insulting you. If she refuses to acknowledge her behavior towards you and does not apologize, start placing distance between you and her. When she comes around separate yourself, stop running in the same circle of friends. If your family and friends are wondering what’s going on, tell them it is not them you are avoiding, but say no more, because you do not want to involve others or stir up more mess.
Do not think that because you are sisters that you owe her your attention and friendship. I had to come to the painful revelation recently that I cannot be friends with my sisters. You can still love her from afar and wish her the best, maybe in time she may mature and feel more positive about herself and mend your relationship, but the way things are now, I would not count on it.