Trying to Fix Her
In days passed he has been there for her, and in days to come, he will still be there. No matter what, Simon will be in her life. River knows this with every fibre of her being. Simon is a good man and an even better brother and once he sets his mind to something he is unstoppable until he has achieved what he has set out to do.
What he has been working on the past few years is trying to fix her. Trying to fix River, the flowing wild, who will never stop running and never stop feeling and rushing over rocks. Voices, calling out, screaming in her mind, like ghosts of memories that aren't hers. Hopeless. She knows even Simon can't help her. Nothing and no one can tame the fury within her and cure the voices she hears but does not own. Not even Simon.
Not enough knowledge in that intelligent brain of his. He's smart, but you can't understand something if you don't have the data and he is missing the data he needs to help her. Only the Alliance has that data. Only the minds of those on the project hold the information they need. Too dangerous to recover, so Simon can't get access it and can't help her.
In days to come he will see it as clearly as she does. There is little hope for her recovery. But on Serenity they have both found a home. They have found their own bites of happiness and until there are no bites left and nothing remaining to lick the last bits of flavour from, there is where they will remain, both of them, together.