The evening this happened I told her we had to get rid of the dog. I didn't aim for her to be away when the dog was given away, just that she was with her father when the exchange took place.
No, it is not normal and does invite concern. It would be wise to arrange a psychological evaluation for her. It is understandable that you decided not to risk the dog's safety. Your manner of doing it, surreptitiously in the girl's absence, was ill advised. You should have been open about it with her vs placing the dog and then telling her about it. Such sudden and unexpected losses are not good for kids (particularly in this case, when her behavior resulted in the dog's departure).