Mid-life diagnosis not accepted by siblings causing conflict (trigger warning!)

Hi, I don’t usually post to forums much as I’m frequently mis-understood but I feel the need to seek help with my current situation…

I have 2 siblings (both a fair bit older than me,) and recently our Father passed away. Our Mum also passed away some years ago.

Last year I was given an autism diagnosis at the age of 49 which amazingly made life suddenly make more sense to me regarding my feelings, behaviours and mental. My siblings seem unable to accept this and the eldest refuses to see how her behaviour makes me anxious and upset which then causes me to withdraw from her and the situation. She has to have the last word on everything and uses my mental health to manipulate me. 
We are needing to work together to sort out our late Fathers estate after his passing, including his house which is to be sold and split between us. When we are all at the house to sort through things it gets loud as everyone (including spouses,) all talk over each other and the volume goes up, I can’t get a word in edgewise which leads to me feeling overwhelmed so I retreat either physically or verbally. 
The other week there was an issue with the gas pipe at the house and she asked me to be there for the emergency gas engineer which I did. He found a leak and capped it off saying that there was some faulty soldering that needed to be fixed. I relayed all of this to my sister who then got a gas engineer who works for them to look at it and he said that he couldn’t find a leak but that there was gas leaking from somewhere but it was within legal limits, so he reconnected the gas. I felt concerned about it being reconnected knowing there was a leak, legal limits or not, a leak is a leak and should be fixed I think. My sister didn’t even listen to my point of view and just threw facts at me about how good her engineer is. This caused me to retreat again and within a few days she was emailing me saying had she done something to upset me and that she was worried about me. I told her not to worry, I just feel like my voice isn’t heard sometimes and that part of my autism means that I retreat like this when I’m overwhelmed and that I needed a few days break from it. She then went on a rant saying how I should take over everything if I felt like that and she was only doing this because she’s concerned about me and that my voice is heard (it isn’t,) and how I was taking everything out of context and overreacting. In the end I stopped replying to her messages and withdrew to take some headspace for a week.

We had to meet up yesterday to sort out our Dads memorial so I took the chance to try to calmly explain that she shouldn’t worry about me and that I can’t help the way I retreat because it’s just my way of dealing with things. She exploded at me and wouldn’t even listen to my explanation saying that she told me that she was getting their engineer to look at it and it’s within legal limits, I said ok but I just thought that… she didn’t even let me finish trying to explain my concerns and was shouting at me at this point that I should take over doing everything and the lady in Asda had told her that I said she was bullying me. I pointed out that I hadn’t even seen that particular lady since before our Dad died and if she’s said that, she’s either outright lying (which is something I really hate, I just don’t understand why people lie,) or she misunderstood something my husband said about me trying to make my voice heard. She then dissolved into screaming that not what she had been told..blah..blah I struggling so I said “this is exactly why I don’t talk to you and feel unheard and overwhelmed” she continued shouting and ranting so I went into meltdown and walked out.  
Now I just feel drained and exhausted and I think I will need to cut all contact with her except anything to do with Dads house. She just seems to completely brush off the autistic side of me that gets easily overwhelmed and how persuing me with hostility results in my meltdowns and harms me. She seems to think that because I wasn’t diagnosed as a child that it’s not true and I’m making it up. I just don’t know what to do, think or even cope with it all. I’m questioning myself if it’s me causing the problems, what’s wrong with me, why doe it always end this way…. I just feel confused, angry, upset and helpless.

If anyone could offer me some advice, I would be very grateful.

Thank you and apologies if this affects or triggers anyone else.