Firstly, well done for keeping your feelings to yourself, and for recognising the issues at play.
I worked with children & families with ADHD & other specific learning difficulties. Many parents end up with anxiety that spills over.
Yes, 13 is a tricky age, but even more so with ADHD in the mix. One of our DGCs with mild ADHD became very anxious at this age, about being away from his parents - despite having stayed enjoyably with both sets of GPs, other family members & friends since he was 3 years old. We saw this anxiety bouncing between him & his parents, but with time & understanding it resolved itself.
You say you won't offer again, but when & IF you feel able, can I suggest that you have a quiet word with your DD? Simply say that when the family are ready, you would like to organise a trip.
I'd also like to make another suggestion that may or may not not be suitable for your family. Many kids with ADHD, especially teenagers, get on much better with an activity holiday - whether an organised kind or simply being somewhere they can swim, run, do a lot of active stuff.
And this is a good place to vent anonymously! I hope you enjoy your trip, and that the family find a way to negotiate this.