I don't think YABU for the way you feel at all.
It's really hard when one of your children is behaving that way and not beeing nice to they're siblings and we've been going through the same OP,you have my sympathies.
We have 5DC 3 DS 19,17,14 our youngest son is autistic and 2 DDs 12 and 8 and our youngest daughter is also autistic.
We took 4 of our Dchildren away(oldest DS was doing overtime at work) this year over Halloween,it was the first time we'd been away over Halloween,we spent a small fotune,best accommodation,full board,new costumes for everyone.This country not abroad,I think that would have made me,DH and the rest of the children feel even worse.
DD12 was a complete and utter nightmare from the moment we got there pretty much till the moment we left and she had really wanted to go there as well and there was plenty for all of the children to do there.
She'd been playing up alot for a long time before we even went away and my DH said we should cancel the whole thing,I really didn't want to because I didn't think it was fair on the rest of the children and we would have lost all the money we'd paid for the holiday as well.
Oh God she was so bloody awful I actually had a few people come up and ask me if I was okay after she started on me one evening over nothing.
The next evening she pushed her Dad to far and he ended up walking out of the Restaurant we were in with her and took her back to the hotel whilst I stayed with our 3 other children that were with us.She'd eaten and DH had managed to eat and our other children who were with us were in the middle of eating but I'd had to deal with so much with her that evening that I hadn't managed to get any food let alone eat.
Her behavior really did spoil alot of the holiday for the rest of us,I didn't care about how it affected me but I did feel really awful for for our 2DS and DD that were with us and for her poor Dad who'd had to drive for hours to get us there.
One thing that we have found that's been working lately is that if she starts being negative towards her siblings,DH and myself we just ignore it.She really dislikes not getting a reaction,so not reacting,giving her a time out,bed early ect all those things that would end up with her screaming the house down us just not reacting to it seems to make her calm down alot quicker and she now actually tells us she's sorry and seems genuinely remorseful which is a big change.
I hope your DD's behavior starts levelling out soon for all of your sakes including her own.