I assumed she had survived in the snow but was shocked when I found myself telling the Emperor that she had died.
The positives in the game included a snow fight with her, getting her to meet the sorcereses on her own, going with her to her friend's grave, and telling her "go for it" in the lab. That is four positives. The only possible negative was me accepting 2000 coins from the Emperor but Ciri was not with me so she would have no idea that I was paid.
Could the final dialogue options with her have played a part in her dying? If so, I wonder whether I can re-load a previous save
as long as it does not mean fighting the Wild Hunt again.

I didn't take her to the Emperor at all... Therefore the money wasn't offered to me and he didn't get a chance to talk with her.

So she didn't think i sold her and she wasn't offered to become an Empress.

Don't know exactly however if this is the reason why she survived at the end.

I went to the inn at White Orchard and there she was very much alive. She asked if the Emperor believed me.
This indicates that Ciri and Geralt had agreed that I tell him she died.
Nowhere in our conversations did we discuss what I was to tell him.

That and also bunch of choices affect what happens to Ciri during ending. All those Geralt & Ciri moments after Kaer Mohren battle. If you are supportive to her and let her be indepented, she survives.

Well, obviously, Ciris' only way of live must be the one of the empress.

She has no mutations and augmentations, so how she will track things like a witcher does!?

thanks for the spoiler

He's clearly a troll.

A troll???

After all this time I assumed that most people have played through more than once therefore aware of the various game endings. If this is your first play through then please accept my humblest apologies.

It's ok - the list of games I have actually finished is very short. Too many games and too busy a life.

Well then. Troll indeed.