A couple of days back my sister just dumped the responsibility of our lost dog on me as she went up the stairs. She didn't apologise.
The next day we were in the kitchen with my mum and she was discussing her play and mum said to me are you going? I was thinking of what plans I had and then my sister turned to me slightly and said "well, we got you a ticket so..."
Then the day after that she came down stairs and said nothing to me and so I decided to ask her to stop being rude to me. She pointed out to me that she was stressed with the dog thing and that the other stuff wasn't her trying to be rude.
I told her that it was no excuse to speak to me like she did on the stairs just because she was stressed and that it wasn't unreasonable to have the suspicions that I had when she didn't apologise.
She slammed the door behind her and I had to shout because she likes to raise the speed and volume of her voice.
I feel guilty for shouting at her because she gives that impression quite well despite her being the only person being unnecessarily rude but at the same time I didn't involve my self with her, I didn't chose to interact with her whilst she was stressed... I was just minding my own business and if I was stressed I wouldn't take it out on someone unless they got in the way.
What should I do? I've tried to ask her nicely not to do things in the past and she's just gotten all sensitive and defensive about it and I've come to the conclusion that I have to be more forceful and let her know that I'm not something at her finger tips. How do you let sensitive people know that they're being annoying without hurting their feelings?
I kinda have to reassure myself that I'm not being mean with her when she's the only one who's encouraged getting confrontational and that strikes me as a little bit cold and sly; causing confrontation and then making you feel guilty about saying anything about it.
I'm really at a loss to be honest about how to act with her.

