Just chiming in here...I wasn't keen on buying a snake for my two boys. But as a mom, I broke down and allowed it. Now I am more involved with the snake and am even getting two more hatchlings soon. I think what has made me so interested in it is the biology/science part of it. My boys are learning so much from us having the snake and they are only 3 and 5. Eventually, when we do decide to breed the snakes, it will be more for understanding the lifecycle of the snakes and some basic genetics as well.
Perhaps if you can tie owning the snake into something with school or your science teacher, your mom will realize how taking care of the snake is very educational as well as responsible. One other thing to show her how responsible you will be might be to volunteer at a reptile store to help care for the snakes. I met a young boy at a reptile store that comes in, feeds and handles the snakes a couple times a week. Good luck.