Is there such a thing as cheating on your teacher?

I have been studying Ashtanga with the same teacher since 2009.  My teacher is authorized through KPJAYI.  She is a really good teacher and I have learned so much from her.  However, as my passion for Ashtanga deepened, so did my desire to meet other teachers through workshops and other events.  Over the last year, I took workshops with Kino MacGregor, Tim Miller and Lori Brungard.  I also plan to travel and study with Sharath.  This leads me to a question that has been bugging me for some time.

Is there such a thing as cheating on your teacher? 

My teacher was unhappy that myself and two of my friends went to see Kino.  I do understand part of her point, that you should only have one teacher or else you will become confused by conflicting guidance.  But that isn't the only reason she was upset.  She believes that since she is authorized, she should be enough for her students and they shouldn't want or need to look elsewhere.  Am I breaking some ethical code by occasionally studying with another qualified teacher?  I still intend to study full-time with my original, current teacher; but sometimes, I'd like to meet and learn from other teachers as well.  Each teacher has different strengths, and by blending their teachings together, I feel I have learned a lot more about yoga.