But she feels crushed by the sad reality that even though she now loves him as well that it doesn't change the fact that he's dead, so everyting it's too late now. That depression probably affects her mental concentration which might've indirectly caused her death.
And about Kakashi, maybe inbetween all of those events above he might want to be with Rin (either because he now likes her as well or just to make her feel better) but instead encounters a reluctant Rin who doesn't know what to do with herself thanks to her new found feelings for Obito.
You know, as I was writing my original comment I thought of you, and guessed that if you were around you'd counter with something like this.
As for what you said above, it seems as possible and viable as anything else. Looking through the prism of Kishimoto's parallels, he could choose to relate Rin's posthumous love of Obito with Tsunade's for Jiraiya. But for me, I would rather see Kakashi get the emotional focus. I would like to see that, compared to his team counterparts Orochimaru and Sasuke, Kakashi learned from his mistakes early on and had a heart with romantic feelings for someone even if it was doomed and caused him more pain.
Since Kakashi is an important character and one we've followed from the very beginning, I'm more invested in him and his personal struggles and demons than I am Obito's. I am sympathetic to Obito, but he exists in the story because of his relationship to Kakashi and Kakashi's personal growth. For that reason I look for Kakashi's development first, and think it would make a better story to see one of the characters in the "emotionally cold" role grow and experience a true, sacrificial, romantic love.
That would be interesting, and would go a long way toward salvaging the kind, thoughtful Obito we met in the Gaiden.
Yes, he said he would have left her back when he was a kid -- before the harrowing experience of losing Obito because of his mistaken outlook and hesitation to help save Rin.
Kakashi was a victim of prejudice and scorn because of his father, and he was trying to do the right thing and do it by the book because he was young and inexperienced. It wasn't that he didn't care about Rin, or didn't have it in him to love her, it was that he was struggling to overcome the suffering he had already experienced in his life and was confused by his priorities. Everything we know about Kakashi now proves he was profoundly changed by Obito's nindo and sacrifice.
We should think carefully before judging Kakashi for an attitude he had in childhood -- before he learned a painful lesson and had his eyes opened. We should think carefully before assuming Kakashi's heart, maturity level, and viewpoint remained so unaffected that he could never have loved someone who loved him. That's what a lot of people say about Sakura, and why they say NS will never happen.