Hi guys,
It's a long story and believe it or not this is the shortest version I could write
. I had my younger Sister come stay for a night and she brought my Niece who is 2. I see my niece very frequently and shes very close to me.
Both myself and DH smoke (I know, very bad but I have cut myself down recently from 10 a day to 2 and I'm working on quitting). I know some people will judge but it's our home . We dont have kids and would normally smoke in the living room but because my sister was staying we decided as a once off to smoke in our bedroom, I didn't want my niece being in a smoke filled room. The following morning I asked my sister if she would like to have one with me as I was planning to air the room out for the day and had lit wax melts to minimize the smell. She told me she was fine and didnt need one. Later she decided she wanted one and came into my room with a cigarette and I told her to go out to the back garden because I was airing the room out. She argued that I had smoked in there about 6 hours ago and what was the difference now. This really pissed me off because 1. It's my home so my rules and 2. I only decided to smoke in my bedroom so her daughter would have clean air. She just told me to go F* myself and walked out of the room.
So I decided to allow us to both cool down and half an hour later I approached her to talk but she called me a C and said I was just saying no for the sake of it and said that I was a control freak. When I tried to explain that I didnt want my bedroom stinking later she said that if it was her house she would allow me to smoke anywhere and just told me to get the f out of her face and that I was trying to control her. I walked into my bedroom because she was calling me every name under the sun but she barged in my door and said the reason I have hardly any friends is because I need to control everything 
. All the while , I'm telling her to stop shouting at me because her daughter is in the next room and to get out of my room.
My sister has always been erratic but has never followed up on appointments despite family interventions, has been on various antidepressants but wont stick to the medication and has abused various drugs including prescription medications. She can explode out of nowhere but seems to be able to put on a charm in front of extended family so they never get to see the real side that her closest friends and family see. It's been very hard over the years because although I love her and want to be close to my niece very badly , my own mental health has taken a toll just having to listen to her and her problems with everyone else around her. Our family GP has long suggested Bipolar disorder or a personality disorder which is why he referred her to a specialist but she just wont attend and will go MIA days before the appointment.
At what point does somebody question whether it's the persons mental illness that had them behaving this way or if they are just being an absolute tosser?
Was I being unreasonable for not just allowing her to have the cigarette in the room?
Advice would be appreciated guys xx