Definitely sounds like something is going on in your relationship with your twin. My twin lives over three hours away. We made the break after college when we went to different grad schools.

Can you afford to talk to a therapist about her? If she is being controlling, then that's a red flag. It would be best if she went with you. Would it work to tell her you're going to see a therapist (not saying it's because of her) and would she like to go with you?