If you aren't afraid of being vulnerable about it, offer her your goals/why MBA essay and ask for her feedback. Maybe reading it will give her confidence in your conviction. I daresay it may even strengthen the trust between you two.
Career goals were never something I sought to share with my parents. (I tend to think of them as old-fashioned, and their advice about as relevant today as disco hotpants and platform shoes. :D) But I surprised myself by sending my essays to my father. It wasn't to get useful feedback, but moreso for
his benefit to understand the motivating forces that are driving me to give up a well-paying job with upward mobility, and uprooting myself in order to move to part of the world where I have no experience in... to pursue an MBA.
Your essays will inevitably be very personal. And it would be very difficult for anyone, especially a parent, to stomp on your career aspirations after reading such an exposition. If you aren't afraid to share, maybe this is the way to go. It's also much easier to have someone read a complete development of your thoughts on paper, instead of communicating by conversation where you risk being interrupted or having the subject derailed.