First of all, let me say that I agree with everybody else.
Secondly, I had the same predicament as you do. I was (and still am, unfortunately) living with my parents. The first time I brought up the fact that I wanted a snake, my Mom told me flat out NO.
I respected her decision, and waited. I would get on the computer which is in the living room, and look at nothing but snakes. Seriously, for a year, I was at this site as well as any other snake site I could find every time I was online. Eventually, she started gaining interest, and she would ask me what kind of snake that was, and how big it grew, and so on. She took interest in what I was reading about. I explained everything I knew about snakes to her, and told her about Corn snakes. She asked me how big they grew, and I told her - she freaked out when I told her 4 - 6 feet, but I explained to her that they don't get girthy.
Then, I asked her again if I could get a snake. She told me that if I want one, it would be with my own money, and she would not pay for anything. I thanked her, and when I got my Economic Stimulus check, I went out and bought a snake.
I never forced her to hold my Corn. It was quite the opposite, actually. Rarely did I let her even see him because I knew that she was afraid of snakes. (She told me the reason she feared snakes was because of their tongue flicking. LOL - I explained to her that it's how they smell. I think she's still a little freaked out.)
Eventually, she would ask to hold my snake for short periods of time. I would let her hold him, and as soon as she didn't want to hold him anymore, I would take him back. She's really come around after actually learning about snakes.
She's come around so much, that she and my dad actually bought me a Black Milk Snake for my birthday. It took a year for her to come around, but it was definitely worth the wait.
If you want a Corn that bad, then I would recommend teaching her about snakes in a non-invasive way (like taking her to the zoo or having her look at care sheets and information online), or wait until you're living on your own. Hopefully she'll come around for you like my Mom did. I'm truly a lucky person. Good luck.