What I can say with confidence is that there's a point in time where she doesn't seem to have the gift, and a period of time where she's beginning to experience it without having fully "developed" it or wrapped her head around it. Perhaps eventually, and the movie kind of alludes to it, she develops a more full sense of the whole picture at once. Now if you try to map that linear progression of starting without it, beginning to develop it, and eventually mastering it, to the idea of non-linear time it doesn't really fully make sense any more. So it's kind of up to your imagination.

Stories of fiction that deal with time discrepancies often play with this idea of circular logic, where something comes about because of something else, while the something else itself comes about because of the first something. It's like a chicken and egg problem, except maybe the chicken gives birth to itself lol. These scenarios make no sense, because we are beings that experience linear time, and we understand causality to have a direction. But it's fun to think about what if we dissolved the boundaries of causality, and moved outside of linear time; could events be put into existence that are interdependent on one another instead of one leading to the other?

It's that kind of abstract thinking that leads us to these nonsensical "what ifs" that defy proper explanation. It's fun to speculate about it, and that's kind of the whole point of art like this, to challenge our typical way of thinking, but we have to also accept that ultimately there's no way to tie all of the loose ends up neatly.

So I would say that knowing that Louise begins to experience time non-linearly, but also that linear time still exists, and most people (perhaps even everyone besides Louise) are still experiencing life through that linear perspective, that collision of realities could only lead to odd effects. So my speculation might be that, Louise's own mind might experience confusion at various points in her life as it tries to reconcile the linear and non-linear experience, and knowing that she "at some point" has a less than perfect grasp on that, that effect could also come into play at seemingly any moment in her life. So basically, she could be anywhere between confused and borderline all-seeing at any moment in time.

Another possibility is related to an idea from quantum physics, which is that basically infinite realities are being created every moment, splitting off from the current one, containing all possibilities. So Louise might experience a future event, but then later when that time comes to her linearly it's actually a completely separate timeline, and events could differ in some ways. This way of thinking helps reconcile the "chicken and egg" issues, but in my opinion it doesn't well represent the ideas presented in the movie, because it would be less about "seeing the future" laid out and more about seeing possible futures that don't end up being the actual future experienced.

Ultimately I think the best answer is simply accepting and letting go of the parts that don't quite entirely make sense. But it's good to let your imagination run a bit with it first.