Thanks for your response OP.
Things were strained between you already ….you don’t say why.
Nevertheless, you both agreed the activity and the accommodation so you must have been communicating effectively at that a point.
All good and hopeful for a nice holiday so far.
But then, even though all was good, after she had paid her half of the activity costs, you decided not to reciprocate by paying your half of the accommodation costs until you had had a meeting to discuss your relationship.
So she thought all was good, hence she paid up in good faith, but you suddenly wanted to discuss your relationship as if you were blowing hot and cold.
Can you see how that might feel to her, especially if things had been strained previous to all this.
Maybe she just didn’t know where she stood with you any more.
Maybe SHE was perplexed and hurt at that stage, thinking you weren’t going to pay up until you were satisfied with her explanation of herself and the state of your relationship at the extra meet up.
Maybe she was simply over it by that stage.
And as she had paid for the accommodation, and you hadn’t reimbursed her, she decided to go with her husband.
As for wanting to do the activity with her husband, maybe she didn’t know you had cancelled it. She had paid you for her half after all !
I wasn't berating you OP, just trying to find the facts in order to help you, as invited by you, to decide if you were being unreasonable to think you had done nothing wrong. We can only go on the information you provide and it’s normal to ask for background info.
For the record, I still think you should have paid your half of the accommodation asap, regardless of you suddenly wanting to discuss your relationship.
It’s only fair to keep things square even if you were miffed. Not doing so doesn’t help, it makes things worse.
It seems to me that you deliberately withheld that payment until she met a new condition that you suddenly imposed….to meet up to discuss your relationship.
So, I’m afraid to say that I think YWBU to delay paying.
That is what you did wrong.
Also for the record, I think she was wrong to blank your messages even though she had had enough by that stage, and could have been thinking, my goodness this friendship shouldn’t be this hard.