How to deal with a difficult sister who thinks the world revolves around her

[NuclearEnergy]

I kid you not, she has seems to think the world revolves around her. She is very narcissistic to start. She brags about how she treats people like crap. Apparently she got her old job back as being a waitress and was talking about how she told a customer to shut up last night. And apparently she can't get fired at this place she works at. I really think karma is going to come back to get her pretty hard. Or there are instances where she talks about how at clubs she is getting is someone's face and telling them to shut up or something and everyone is cheering her. She also told her friend that she has a Bachelors degree, when she actually has an associates degree. [I was in the car with them]. As someone who is a year away from achieving that, this really bothered me. She is just very rude and obnoxious. And yet, whenever she is over my parents give her all the attention. She also is very disrespectful to me and my older brother. We aren't social butterflies like her, but since we don't act like she expects people to act she is snobby towards us. She brags about how everyone at parties want to hang out with her and such.

She is also really into fashion and wearing the latest trends. Me on the other hand? I have been wearing the same thing for the last 4 years. T shirt, tan cargo shorts, black socks and vans. However, one instance we were on our way to a family gathering; I got a bloody nose. She proceeded to notice I had some on my arm. So me being thrifty and there being no sinks nearby I just licked my finger and rubbed it off. My sister yells: DON'T DO THAT! THATS DISGUSTING!
Another instance at my grandpas funeral  she made my older brother cry at our grandpas funeral because she told him to stop putting flowers on our grandpas casket

I don't know, it is just really bothering me. She is 26 now. But growing up my parents had the approach that they should just let her do what she wants. Because they feared if they gave her rules than she would leave them and never want to talk to them again.