How to point out to my friend she is being a *****?

one of my best friends and i got really close over the summer and i was her best friend ( she was kind of lke my second best friend??) and we had good times and we were always really nice to people. now that school started she acts so different and i noticed this last year too. when were around other people she trys embaring me or making me look stupid. she roles her eyes or ignors me everytime i say something and even though she tries proving me wrong everytime i say something shes like "yeah, your ALWAYS right" even if i am in the situation. i want to point out that shes being a ***** and i cant stand it but she mocks everything i say especially when im being serious, or she makes fun of it with other people. idk what to do or what to say to her