If they bring Choudhury back from the events of this novel, I'll start calling BS as there's nothing there to hint it's possible. No memory backup, no katra, no friendly Q after a travelling companion, no temporal shenanigans...
Don't worry. She's not a TV character. There won't be legions of fans asking "where's Choudhury?" or saying it doesn't feel like a TNG book without her. There's no pre-established audience with an interest in her to be prompted into buying books on the promise of a new Choudhury story.
I wouldn't worry about book-only characters returning from the dead; even someone like Vaughn, who was as important and notable as a book-only character can be, I can pretty much guarantee we won't be seeing again. It's the TV characters who are considered integral parts of the original shows who we can't be assured will stay in the grave.