Panic attack last night

I am still having to stay with my sister at night. It is frustrating, I don't like doing it and she gets upset because I don't like doing it and so acts annoyed and is crabby. So I get crabby and she tells me she will call her social worker because I am being mean to her.
Last night it was too much, I had taken it too long and was stressed and had lots of little things I was dealing with and so I told my sister she had to stop threatening me with telling on me, because I don't have to be here. I was doing her a favor and don't have to come and so there is no threat of your social workers getting me in trouble I could leave if I wanted.
But she wouldn't let off and so I tried to go into another room and calm down, I had been raising my voice to her and was getting angry with her. But I couldn't stop the frustration of the situation that I didn't have to be there but at the same time I did, I was the only one she had who could be there. I want to be in my own home and sleep in my own bed and having her tell on me and get me out of there would be the best thing for me. But when I said I didn't need to be there and could leave she then said she wanted me there. That she dint want to have me not come over anymore. so I told her to then give me some space and be nice. and she turned around and said she dint have to.
My sister is developmentally stagnated at about the age of 10. So it is difficult to reason with her at times, She gets tantrums and stuck in an attitude and can't change it very easily. It usually takes time.
But I was on the verge of a fugue anxiety attack and couldn't go anywhere and couldn't calm down with her continuing her fit. So I went in to a back room and started crying uncontrollably. I was stuck not being able to leave and at the same time not really needing to be there and her wanting me there but not wanting me to be able to be even a little bit crabby about it.
This scared my sister. I had never had an anxiety attack in front of her, I had always been able to stop it before it got really bad, only at the heavy breathing kind of quiet meditative state. But when I started the uncontrollable sobbing and then couldn't breath and couldn't stand still and had to pace around the house, she came and tried to comfort me telling me it would be alright. It got her out of her tantrum but then made her anxious. so we kinda consoled each other.
It wasn't one of my worst attacks. It wasn't even all that bad of one. But it had been since Friday coming. It felt much better after it was over and maybe my sister learned that treating me as if my feelings didn't matter might have consequences.