What you have is a trained reflex. You ignored her for years while she adapted to whatever suits her. In a sense, she has gotten her way and ended higher up on the totem pole. Parents may or may not have exacerbated this but everyone seems comfortable with the status quo.

Your solution to the matter early on is out of sight, out of mind. All of a sudden, you're not happy with the status quo and want a fix. It's not realistic.

If you expect to have a conversation and be listened to, perhaps you might want to bring your parents and/or sister out for a sit down. Being at home wouldn't work because familiar settings just allows people to regress back to their practiced reactions or retreat into their safe spaces such as a closed room.

Have a think about what you want and convey it. Preempt and ask what your sister wants as well instead of allowing her the opportunity to use antagonism or passive aggressiveness to respond. Sometimes people feel comfortable being an asshole, not because they enjoy being one, there's a difference! Control the outcome where you can.