The snake will be kept in a locked enclosure so theres no chance of it getting out correct? I would ask them to come up with some ACTUAL reasons why they dont want her in the house. Try explaining its your passion and even tho they dont see her as a pet you love her.
If they still refuse i would get your own smaller/cheaper place and say screw them. I cant imagine parents refusing and pretty much disowning their own daughter over something as stupid as this. At this point i would completely stop talking to them. If your dad says something like, "oh you really wanna make the stupid decision of keeping your snake instead of moving in?" i would snap back with, "id rather live with a stupid snake than with stupid people."
This^ is all what i would do, not saying you should though. I can be extremely stubborn and emotionally unnattached when it comes to people pissing me off haha.