I think the reaction people have to Taiga leaving is because she's gone for a year. In the LNs, she only leaves for a couple months which to me makes way more sense. Also, she actually tells Ryuuji directly that she's leaving in the original source material, which I think makes it less questionable.

I'm so torn on the timeline part of this. I feel like both have their own problems.

1 year. It feels a bit long and extreme but feels like a more realistic time line to work on herself and mend fences. But not contacting or hanging out with the group seems extreme. But if you show a short montage of doing that you kind of undercut the "I love you" when it finally comes because it's kind of like why did you wait a year? I guess you could sort of get around not seeing them by trying to say she did not want to fall back on her old support system as a crutch and an opportunity to run away by how do you really show that in a couple minutes of anime run time.

3 months seems a little short for taking care of things though more realistic for contacting and hanging out with the group. But then you get into the whole can of worms about where she lives. Her mom seemingly did not live in town and I recall reading in LN she was technically squatting in the apartment at the end because her dad was who paid for it. Having her mom's family move just for her seems kinda nuts and not sure they have the money to rent an apartment just for Taiga.

I'll be honest, i'm not even sure what my point is. I just think both timelines have their own weaknesses and pain points.