How can I make my mother understand that I am going to be a musician and won't ever study anything "real" to get a "real job"?

Enough! She’s driving me crazy with all the complains and stuff, I can’t take it anymore, I would leave and go live somewhere else if I could (but I go to highschool and don’t have any money).

I’ve been taking guitar lessons for almost a year (yup I’m still at the beginning) and I’m going to start having lessons at a conservatory in a couple of weeks. In order to learn more, and get to know other musicians and how stuff works in the realm of music.
Um.. I love my electric guitar (and am interested in genres such as metal, rock, blues, a little jazz, but mostly metal, the heavier the better :p) and I can’t even imagine my life as a non-musician.
My mother wants me to study music at the university we have here, and I agreed at first, but now that I’ve made a little reasearch I know I don’t want to go there. It’s too formal and classic and NO.
(I appreciate classical music, I love listening to Beethoven’s 5th, or Moonlight Sonata and I’d love to learn more about classical music. But later, when I’ll be a musician who already knows a lot and has a lot of experience. I want to start my life as a musician with the genres I like the most, not just a genre I respect.)
What I would like to do is: get the harmony degree, then continue having lessons (at the conservatory I’m going to go to) and when I reach a certain level and be able to play really fuckin well, make a living out of it.
As I said before, I don’t want to be anything else. How can I make my mother understand that? (my father understands. not 100%, but he does. He used to be a singer and I sing too, and didn’t ever go to university). She keeps telling me to study something. Well, I’m studying music, but I don’t want to go to that university she seems to like so much. She studied something that wasn’t her dream and did nothing in her life. She didn’t have a dream. I’m totally different than that, obviously.
I found a place where I can study photography, which I find a little interesting, just in case… because it’s something I would like to do, but it’s not the main thing. It’s not my life. If I go there, it will be just something more like a hobby.

Um… how the fuck do I explain her that I am who I am, will do what I want to do, no matter what she thinks? And how do I cope with all the pressure? It’s not just that she insists I go to university, she also says that I ”must” study something “real” and not music. HELP.