Unless it's an exclusive right of residence, then it's a sharing situation. However, residing in a dwelling means more than just sleeping there, so your sister couldn't limit you to the bedroom - you'd have to be able to access the bathroom, kitchen living room etc, and you'd be able to have visitors. She won't be able to sell the house without making suitable arrangements for somewhere for you to live
Given the apparently bad relationship between you and your sister, would it be worthwhile to consider asking her to buy out your right? I'm not sure how it would be valued, but a solicitor could advise you. With the money you could rent or have a deposit towards a place of your own and not have to live in such an atmosphere. Her incentive is that she won't be able to sell or raise a mortgage while your right exists without her consent.