Im just ranting y’all, advice would be appreciated tho

My Eldest sister is my current problem. My family and I live in a two bedroom apartment. I share my room with my 3 siblings (one is currently overseas now) and my parents have the other room. My Eldest sister currently has no job and just stays at home these days. I have a job and my other sibling is still a student. This biatch (the Eldest), whenever she want to go 'out' with her friends or whatever, locks the door to our room. Now this wouldn't be such a big deal if she took maybe an hour at most.
BUT NOOOOO
SHE LOCKS DOOR FOR 3-4 HOURS A DAY