Hey iSnake,
Maybe in the future you can work up to a snake with very careful planning. You could continue researching them and learning all about them and maybe using your own money to create a good living space for one, and when your mom sees your dedication over several weeks or months, she might be more open to the idea. A lot of fear for parents when it comes to pets is that you will lose interest in it and they will have to take care of it because it's then too late to take back to the store. But if you show your mom that you truly love snakes and that you're in for the long haul, that may be worth something. It's one thing to get a snake on a whim and have to worry your kid will be bored with it in a few months and another thing completely for your kid to be really into something for a really long time. That's how I got a horse when I was young! It built up slowly from obsession to riding lessons to half-leasing to my own horse--and a horse is a much pricier investment!
I am really sorry about Hershey, though. It's always painful to part with a pet.