How do I quit the cheer team? When I can't stand the coach?

My Coach is bipolar. Seriously she will say one thing one minute and want us to do the exact opposite then next. I can't stand it my best friend is on the team with me and my coach doesn't like her because of her mom and something that happened between them. One day she told me I shouldn't be friend with her. I told her that kind of wasn't an option because she is my best friend and so my coach tole me she was going to tell my mom and dad on me if I continued to be her friend. I told her to go ahead because my parents love her, she isn't a bad girl she is like a really good girl so she isn't a bad influence on me. When my best friend isn't in the room my coach will talk $hit on her and make up these lies and tell us all things things that aren't true. Either way tho she is the adult she is the coach and talking about one of your athletes to the rest of the team is extremely unprofessional. She will tell us to confront girls if we have a problem with them one minute and when we do she tells us we cant to it. If things don't go her way like the boys loose or something she gets mad and goes crazy. When she's mad she yells and makes no sense and rambles on about random $hit for a solid hour or two and we all just sit there like wow. One of the girls has already quit and every one on the team has talked about it. I have been thinking about weather I wanted to for a few days now and I have decided it is whats best for me. I'm going into her office to quit today. What I really want to say is "You are the most unprofessional coach I have ever encountered in my entire life. You act like your a teenager when in reality your 40 who cares if this girl breaks up with her boyfriend and then gets back together with him the next day. She doesn't let that effect the team but you do. You need to do some serious growing up before you can even begin to be a successful coach." Then I would put my uniforms down on her desk and walk out. Now I know that's not okay to say but what could I say that is along those lines and is kind of an FU to her? P.S I'm a senior and I've been putting up with this my who high school career and I can't take it anymore.