blocking your sister on facebook is okay -- just because you live with her doesn't mean she can be all in your business.

I don't know your situation, but, I'm thinking....

maybe your sister is taking on the role of parent? trying to look after you, accommodate you, and maybe, if you've been diagnosed with a mental health problem and on medication, maybe she feels she needs to keep an eye on what you're doing.

maybe she's always been looking out for you, or feels like she has, and maybe she doesn't always want to and gets a bit resentful sometimes.

maybe she thinks you're not able to live independently, and she has to keep an eye on you to keep you safe and well? Sometimes, if people have been ill, we mollycoddle them, wrap them in cotton wool, and as the person gets better and gets more independent that cotton wool wrapping feels like suffocating restraints.

sometimes, people who seem to be wanting to control you are not doing it because they're bad and want to harm you -- sometimes it's just their clumsy way of trying to help.

If I was you, I'd have a proper talk with her. She could be a great ally in your life.

However, if you've already tried all that and got nowhere, how about making a proper plan to get a place of your own?