Absolutely not, the closer to rock bottom she is when she wakes up from her coma, the higher the catharsis factor will be when she claws her way out of it, having become a changed, more healthy person as a result of the alternate past she lived inside her head.
Her life before the accident wasn't so fucked as to be objectively unrecoverable, and it's important for the story to reflect that.
I see where you're coming from, but at the same time I can understand why others might find it frustrating if 90% of the story and character development was undone. Like, even if Koharu remembers everything that happened and is able to fix up her life in the present, what about characters like Yuuko or Asuka & Mutsumi?
Maybe they figured out their problems on their own, without Koharu, or maybe they didn't and Koharu has to come around and redo everything in an abbreviated version of their actual arc. Either way, though, isn't that kinda lame? Either they have no connection to Koharu and won't have the same relationship with her as they did in the rest of the story, or we just end up with a worse version of an arc we already read.
And these sorts of arcs about Koharu helping various classmates is kinda like half the point of the story, you know? Even if Koharu's own story gets a happy ending, you can't just ignore everyone else and everything we've read about them. That can't all just come to nothing.
I don't necessarily think that she has to wake up in a new future sprouting from all the changes she's made, (which I don't really feel is the direction the story is going in, anyways,) but I don't think that just disregarding everything and having Koharu fix her life from scratch really works as an alternative.
Maybe instead, she wakes up in her old world, but the people she helped manage to recover their memories of the alternate timeline somehow? Or she does "wake up" and disappear from this world, but we follow everyone from this world rather than following her back to her original world, seeing how they fare without her.
I just don't really think that you can undo as much of the story as you're suggesting.