"misnomer"?

My evening of horror transpired as follows:
While sharing a bottle of wine with my girlfriend I was stupid enough to posit why it was that I had taken such a huge interest in blues music.
"Why, because it's accessible to your mediocre guitar skills," she said, "and when your skills improve you switch to real music, like classical guitar".
"Well then, I hope, once your skills improve in belly dance you'll switch to real dance," I responded, "besides it is a misnomer that blues is 'simple music'!"
Now, my meaning here was that blues music has been historically labeled and designated as "simple music" in order to mislead people into thinking that African-Americans, from whom the music generated, are not capable of anything complex and so somebody will say, "I love African-Americans because they play 'simple music'!"
My girlfriend claims English superiority because she went to college and has been told she has a greater grasp on the language than it's inventors, so she informed me that I had incorrectly used the word "misnomer". According to her, what I should have said was that 'simple music' was a 'misconception' and not a 'misnomer'. I can see the angle where she is coming from and in all honesty I barely graduated high school, but I am sure that in this instance I am correct. My point was that blues was "misnamed" or "mislabeled" in order to mislead and not if it is actually simple music (I obviously believe that it is not and I am improving at guitar, so hopefully one day I will be able to tell) .
In any case, I am currently sleeping on the couch. Is she correct or is it my "belly dance isn't real dance" that has me on the couch?
Mr. Blues Lover
I beg you not to yell at me about any grammar mistake I may have just made. I finished the bottle of wine by myself and I really just want to be right about this one thing.