Asking someone to walk a dog isn't "changing the goalposts"
I completely disagree @itsgettingweird - It's changing the goalposts because when the haircut was booked, she wasn't told she had to walk the dog first in order for her to get her hair cut paid for.
It's asking a teen to take responsibility for a dog that she wanted and agreed to care for.
Which is completely unreasonable in the first place. You don't get a dog based on the fact that a child agrees to walk it and care for it - you get a dog because you as the parents want a dog and are willing to do all the work involved.
She refused to pull her weight so he told her if she didn't do her part he wasn't taking her to the hairdresser.
Yep - so as he decided on that consequence, he should be the one to reimburse the hairdresser. He could have picked any number of consequences that didn't involve someone else being messed around.
No wonder kids nowadays have such bad problems with consequences. Apparently they needed written notice in advance of doing anything.
Except nobody has said that. If he was only ever going to pay for her haircut if she walked the dog, that should have been made clear upfront, not dropped on her with a couple of hours to go.
He only asked her to walk the dog. An everyday chore. Not an unreasonable request and it's not moving the goalposts as it needs doing daily and she knows this!
I agree that being asked to walk the dog isn't unreasonable. That doesn't mean she should be forced to or else she has to pay for a hair appointment that someone else arranged for her.