If someone is constantly angry and likes to aggrivate people do they have a problem?

My sister seems very disturbed and I'm really worried, yeah everyone gets angry but she's constantly agressive and on the defensive 24/7. She demands things, screams at people like a spoilt brat (even though she isnt) and expects everything to go her way and when it doesn't everyone has to know about it. She slams doors and tells people she hates them and screams a lot DAILY. On the rare occasion she isnt angry she purposely aggrivates people to get a reaction to the point where people threaten to hit her and she laughs and finds it hilariously funny. She's bad in school and cheeky with all of the teachers, does she have a problem?