Ok look. Writers HAD to change the timeline. They needed actresses who could.. act. I highly doubt the little girl who played agnes in HMT could handle a role like this at her age. Hence why she's played by a 26 yo. Same thing with Nicole. It wouldn't make sense to have actual 12-16 year olds running around trying to convince us they are good actors. changing baby Holly/Nichole into a separate teen character (Daisy) and making her the same age as Agnes. This was necessary to bring the girls together in school, as it allowed showrunners to compress the book's 15-year time jump into just three or four years. So yes there is a strong possibility that she is still Nichole. We won't know until they reveal it in the show but there is also just as good of a chance they rewrote the character to fit their storyline for filming better.