How was I being rude/bossy!?

Was there a genuine reason for not wanting to do it, or were you simply butting heads with her because you felt that since your Mother was paying the instructor that the instructor was your employee/servant that should be listening to what you say and not the other way around. Understand that if you pay somebody to teach you something that you should do as they say when it comes to that particular subject. It sounds to me like you were acting like a spoiled brat. Your Mother is failing to teach you that you can't always get what you want, and that it is acceptable to simply quit anything the second that it gets tough. The real world is only a few years away kid, get ready, and good luck. With your attitude you will need all the luck that you can get.