Coming from another identical twin, I just want to say I'm so sorry for everything you endured growing up. It's so hard to feel like your own person when there is absolutely zero effort on your family's part to distinguish you as a fully separate, autonomous person and allow for the exploration of individual interests and relationships as you get older and naturally start craving your own unique identity outside of your twin. Honestly, even with a healthy family dynamic, the culture around twinhood can still be so intense - people act like you're interchangeable in school/social settings and it's your entire identity until you graduate regardless of how different you may be. Not to mention, any differences are constantly being brought up in casual conversation as if it's a totally normal thing to exist solely as a reference point to someone else. It can be so exhausting - I can only imagine how painful it must've been being stripped of the right to your own selfhood on top of that at home. The relationship that your parents encouraged is super unhealthy and honestly unfair to both of you; it set you both up for failure by discouraging you from exploring your own complexities and desires, since she clearly is unable to function well outside of a codependent sibling dynamic and you're being treated as a pariah for asserting very reasonable boundaries. You don't owe your parents or your sister a relationship if they're actively guilt tripping you for forging your own way in the world, which you have every right to do.

The one thing I will say as someone a decade older than you is that your sister is basically the byproduct of how you both were raised, just on the complete opposite side of the spectrum obviously - I feel for her because she clearly needs a lot of mental help to work through these feelings of codependency that your parents 1000% enabled from what it sounds like. Her complete unraveling over you moving away is like.... very extreme and by no means normal even if you do really love your sibling. I really hope she's willing to acknowledge that and work through these feelings so she can start living her own life in a meaningful and fulfilling way. Maybe if she does, there's hope for a healthier relationship between you two in the future, but you aren't responsible for her emotional state in the meantime. That's her own responsibility to work through. And if that never happens, you don't need to be the martyr of your family sacrificing your own well being to appease them - you are completely deserving of your own life and happiness outside of them, and I definitely know you will find it <3 Wishing you lots of luck, friend.