SalUK and Paul are correct. What worries me is that the official receiver isn't doing their job properly. They may have no interest in the vehicle but they do have a legal obligation to the people you owe money to and to YOU. Contact them and tell them to deal with
You sound like the sister from hell! Stop and think how you would feel if your brother interfered in your relationships.
If you really do dislike her avoid her but don't be mean or you may also lose your brother. I'm you're a really nice girl so don't spoil it.