Talk to your mom. Ask her to let you move. If she says "no", you've got to wait until you're 18. You're still a minor. Don't put your sister in the middle.
I am not intending this to be legal advice, because I don't know the particulars of your situation. Call me if you would like to discuss this or other isues.
Sign up to receive a 5-part series of useful information and advice about child custody law.