I told her the situation, and she said (I think, but it was a difficult time for both of us, so it’s hazy) to go on the holiday, which I did.
It could have been this part to be honest, you put the decision of whether you attended the funeral or not squarely on her shoulders, and at a time where she really needed you, she would also have felt incredibly guilty making you miss the holiday for her, and she may have thought you would hold it against her, you gave her no choice basically.
I wouldn't have minded either way what decision you made off your own back, especially if you had tried to change the holiday but couldn't, but I'd have resented a friend putting me in such an awful position of being the 'good guy' or 'bad guy', you had obviously made the decision to go on the holiday, but you essentially forced her to say it was okay so you could go off on your holiday guilt free.
Sounds like a horrible time for you both, but I'm not surprised she re-evaluated the friendship after that.