How can I let go of my best friend?

I have been best friends with this girl since 1st grade.10 years later we are 16 and I've noticed some major differences in our personalities and views on life that and lately I always tend to leave her house or wherever we were together angry or disgusted at her behavior, especially towards her parents. She is extremely shallow and thinks she is entitled to everything. She throws a fit whenever she doesn't get what she wants when she wants it. She is extremely rude to her parents who do everything for her and she doesn't have a job- but still believes she deserves everything she asks for and if she doesn't get what she wants she says "its not fair". This weekend i went to the lake with her and all she talked about was how many instagram likes she was getting and blah blah blah. Haha anyway I am just so upset with her attitude and I have talked to her about it many times and she tells me that I am mean, even when she asks for my honest opinion about things. I am trying to get over my own personal problems and she is starting to make things worse. I don't know how to distance myself from her since we have been friends for so long and are used to hanging out almost every day. I don't want to hurt her feelings but I am miserable.