Responses
If I remember right, it's because the story will keep flowing according to the original storyline. If Louise go for Otis' route. Otis will treat Irenea as if she doesn't "exist" or as an "extra". Basically, Otis moving according to his script and forget about his relationship with Irenea.
This is just based on my understanding.
Why did the second brother leave her in the previous timeline again??? I forgot.I mean if she's to choose him now how can we be sure he won't leave her again??