Need advice

Okay guys.. I live with my boyfriend his siblings and today I had enough because his sister.. who is 18 has no respect for anyone. Today she messaged me to say that I have to take her to the store to get something for her brother who could of stopped on his way to work because he works literally right there. But anyways I ended up getting called a bitch from the brother because I told them that I would appreciate it if she would ask me instead of tell me to do things. And I just am at a cross road where I dont know what to do.. I dont start my new job for another two weeks because I got a new one... how should I go about this. I get blocked and treated like shit. And my boyfriend kind of stuck up for me because his sister has no respect for anyone or anything. And I just am in the spot where I want to just give up and move back home...