I wanna get a pet frog, but my sister sorta ruined it for me. What should I do?

My parents don't like pets, but they let my sister get a red-eared slider turtle. They hate it. It smells and it's tank is dirty, and they end up cleaning it. So if I asked them, I know it'd be a no. It seems impossible to change there minds. I really want one, and I'd feed it and clean it. I'm more responsible then her, and I love animals. Help?