She is always watching her daughter be born, watching the aliens fly away, and suffering through the “memory” of her daughter’s death.
This is explicitly depicted in the film when Louise uses different events throughout her life to affect other occurrences, regardless of their non-sequential order. We repeatedly witness Louise interact with events in the future and the present by being simultaneously aware of both. By talking with Ian in 2016 Montana about zero sum games, she is able to help her daughter Hannah with her homework in the future. And again, with perhaps the whole future of humanity (and the heptapods 3,000 years hence) at stake, she is able to discuss with the high Chinese General Shang the details of their fateful phone call from 18 months ago… while simultaneously having that conversation at gunpoint in Montana.
Villeneuve’s film (and the Chiang story it is based on) suggests free will and choice exists if one chooses to do nothing. Time is not immutable, hence why the aliens’ presence on Earth is still high stakes for them. Presumably heptapods have long lifespans if they can perceive events 3,000 years from now, but humanity will only save them if we as a species work together right now to learn what Louise’s future book coins as “The Universal Language.”
As the ending clarifies, Louise has a choice to allow events to occur as she currently perceives them… or to not let them happen in this way, sparing her the pain of losing a daughter she already deeply loves by denying that kid a chance to even exist. As fittingly revealed out of sequence, Louise asks Ian at the end of the film that if he could see the whole story of his life, would he allow events to transpire exactly as they do? He responds with a wishy-washy answer about how he isn't sure right now. But we already know from a previous memory of the future that Louise and Ian's marriage ends because she tells him too early about what she knows. As Louise vaguely explains with paternal love to Hannah, she told Ian about the choice she made, and he thought she chose wrong.
For Ian, watching Hannah die from an incurable disease made their whole marriage, and the whole story of their shared live, unendurable. However, as with most matters in regard to bringing life into this world, it was the woman’s choice. Louise’s choice. She chose to allow Hannah to be born, and as a result, she exercised her free will by enjoying her life story’s organic telling.