Thank you all for responding with your input. I finally got her to actually sit down with me and discuss it, and let me tell her why I thought a snake would be a good pet. Her only argument against it that has stood up after I've talked to her is that she doesn't want to have a snake in her house. Which is something that I don't understand but will have to respect. It was really annoying me that she was making all these excuses as to why a snake wouldn't be a good pet, when I could explain away every one of her points.
Right now the answer is a solid "maybe in a while", which I can deal with. There are some things I need to do first before getting a snake would even be possible, but I asked her now because I didn't want to spend my time and energy preparing for a snake if she was never going to allow one in the first place. I appreciate you guys giving me the idea of taking her somewhere that she could properly see a pet snake, as all she's had experience with are wild bull snakes (which are pretty aggressive). She doesn't understand that not all snakes are like that. She seems a lot more receptive once I told her that a ball python would be unlikely to ever strike at me unless I was threatening it, and that the reasons they have trouble feeding is because it's difficult to get them to strike. The hard part was getting her to listen to me.
And although your stories about having secret snakes are funny to me, I'm afraid that can't happen. She's very... nosy, I guess you could say. She'd probably hate me forever if she found I disrespected her wishes. Her house is also quite small and there's not really any room for me to secretly keep a snake, and since I'm under 18 she has access to all of my bank statements.
Again, thank you for giving me some advice, I appreciate all of it. :^)