Single adult, forgotten child

I (42f) am the fourth born of five siblings. I am single and do not have children. Our parents had their 50th anniversary in March and paid for us all to stay in Florida for a big family vacation. There are 18 of us total - mom, dad, my siblings, their spouses, and 8 grandchildren.
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There are four condos in use. When I asked what the sleeping arrangements would be, I was told I would get the spare bedroom at my parents place and my oldest sister, who is also single and childfree, would be banished to the hide a bed at mom and dad’s. That’s not fair to her so I spoke up, but the issue of where the two single adults would sleep got swept under the rug. I made it very clear that I didn’t want a repeat of Thanksgiving where I had to sleep on the couch in the basement because my 5 year old niece and 2 year old niece “couldn’t share a room” for whatever reason, so the 5 year old niece got a queen size bed that I normally sleep in when I’m in town for holidays to herself.
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Anyway, even though I voiced that I found it unfair that my 50 year old sister had to sleep on a pull out couch, and the two of us should get our own rooms because we’re fking adults. Again, swept under the rug. I wasn’t really asked to be involved in the planning of this trip even though I plan events and trips all the time. So imagine my surprise when I’m getting off the plane and receive a text message with the address of our other sister’s condo because my oldest sister arrived and claimed the spare bedroom that was promised to me a month ago. They decided I could just bunk with my 14 year old niece which I knew would end up happening. This setup also caused her twin brother to get banished to the couch at mom and dad’s.
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My younger sister (the mother of the 5 and 2 year olds) talked to me on the phone about a month ago and said “we’re just not a family that’s big on planning things,” but I clapped back with “we’re fine with planning but we SUCK at communication.” So here I am, an adult, crying on the sofa because I didn’t want my niece to hear me, sleeping on a couch with zero privacy, because I’m the forgotten child. It’s beginning to feel like nobody gives a rat’s ass about me and that really sucks. I should add that I’m likely autistic and definitely highly sensitive and don’t like last minute changes that are made for me without my input. Honestly if they would have told me that I’d be sharing a room with my niece from the get go, it would have been fine, but I think they thought I would get mad if that happened. I’m more upset about the consistent lack of communication and inconsiderate nature of my family than anything else..
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I understand that I should be grateful that my parents can afford to take us all on a trip, and believe me, I am. I’m just getting very resentful and bitter that nobody EVER asks for my input on things. I don’t know if it’s because they think I’ll throw a fit or can’t handle bad news, but in reality, I think they don’t consider my feelings because it’s just me and I don’t have a spouse or children.
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I got to town barely an hour ago and I already want to go home and finally go no-contact.