i think that's dumb of her to assume that you should be as proud of MAC because she is. obviously everyone has their own goals in life, and maybe that's not the only thing you'd like to accomplish as far as professional make up artistry goes. however, i could see some misunderstanding from her end too, though. it could have just come across as though u were saying "i'm better", though i don't necessarily agree that wanting to further your career means you're a snob and insulting people that don't want that, though that's probably what she got from that.
no offense to any MAC employee, but there are clearly people who just have a passion in make up in general and happen to represent MAC, and then there are people who only want to be a part of the MAC world, yet not necessarily with their own clientele.