Caleo
A smoker can choose not to smoke on occasions. A dog owner can't choose to leave the dog tied up outside as someone might steal the dog.
Even if the walking group was a crowd of twenty people it's reasonable to assume one or two of them would be aware of the needs of a minority of one.
So does that mean you would ask the smoker to join the others in the non-smoking area? And if she refused, would you leave her on her own or sit in the smoky area?
I wouldn't leave a dog tied up either, because, as you say, it could be stolen. It's interesting though, that the choices offered by the OP don't include a compromise on her part, which is not taking the dog in the first place. It's all about what the others should do given that the OP's needs are met.
I'd be interested to know why people think that the others should have sat with the OP? As I've said, I would probably have done so, despite not being happy with it, and I've asked myself why. I am a bit of a people pleaser, so that's probably why, but I can't think of a logical reason. It's not about the rules of friendship, which involve people looking out for one another, as if they had been followed the dog wouldn't be there in the first place. It's about who dominates the relationship, really. I am aware that people pleasers are easily exploited by those who put their own needs/wants first, and as I've got older I've tried to stop putting myself in that situation, but the habits of a lifetime are hard to break..