That might be the choice you have, at least if you want a good relationship with your sister.
If you force her to choose, she will resent you. That is a guarantee, even more than the ball dropping on New Years. She may be your guardian, but she is your sister, not your mother. You are 17, and you don't need someone to wipe your nose. Like it or not, you have some responsibility for yourself.
Believe it or not, I love her. I want her to have a good relationship with you, but I'm not going to let you guilt her into your misery. I'm not going anywhere.