I hate one of my best friends.

So I have been best friends with this girl for around 2 years. When I switched schools she was my best friend. But this year she just got really annoying. Like one she stalking her ex by wanted to watch every move he does. Then she is so annoying at school by thinking she knows every answer and things everything is funny. She does the same things ate sports but by thinking she is better than everyone. The next is a simple thing it is just she is hanging on me. I fell that she is always next to me it is sometimes annoying. The last thing is weird but it annoys me when she always asked me if I am okay when I am just sitting there and that is a twice a day thing. So what should I do should I stop talking to her or what. Is This Normal