AITA for refusing to pet-sit after my friend booked her trip before asking me?

My friend Zoe has a beagle named Scout. I have watched him twice, and she has watched my cat once. We never treated the favors as exact trades, but there was an understanding that we helped when we could.

Three weeks ago, Zoe sent me a screenshot of a flight confirmation with the message, “Beach week is official! Scout sleepover at yours July 9–15?”

I thought the second sentence was a joke because she had not asked before booking. It was not.

I told her those dates did not work. My cousin would be staying with me for two nights, and I had tickets to an outdoor concert on Saturday. Scout cannot be left alone for long and becomes frantic during thunderstorms. Taking him would mean reorganizing the week.

Zoe replied that she had chosen the dates because I had casually said I would be home in July. She offered to have her dog walker cover the concert evening and said Scout could sleep in my room while my cousin used the couch.

I said no again.

She found a boarding facility, but the total cost was much higher than she expected. Her plane ticket was nonrefundable, so she paid. Since returning, she has been distant. She says I was not required to help, but a close friend would have tried harder after realizing the alternative cost.

There is history behind that sentence. Last year, I had to travel suddenly when my father fell. Zoe took my cat with only a few hours’ notice. She changed dinner plans and bought an extra litter box. I thanked her repeatedly and later watched Scout for a long weekend.

Zoe sees this as the moment I could have returned the kind of inconvenience she once accepted for me. I see a difference between an emergency and a vacation booked on an assumption.

She says the trip was not completely casual: it was the first time her siblings’ schedules aligned in years. She also says she did not ask earlier because the fare was rising while the family group chat argued.

I could have managed Scout. My cousin likes dogs, and I could have paid the walker for an additional evening if the weather looked bad. What I could not get past was the booking confirmation arriving before the request. Agreeing felt like teaching her that my calendar could be filled by announcement.

Now I wonder whether I protected the principle at the cost of a friendship that had previously been generous to me.

AITA for refusing when I technically could have made it work?