No, Ollie didn't believe that Allie blamed him. She wouldn't ever blame him for something like this. "I know you don't," he said softly. But I do, went unsaid. He almost winced away when she went to kiss him on the cheek because that was not taking care of herself like she'd promised Ollie that she'd do. But he didn't have the energy, and he was grateful beyond gratitude for the show of affection from his favorite person.
"It's always good," he told his sister quietly, reaching down and taking her hand, feeling tears springing to his own eyes. He didn't want to say goodbye, formally. Because he knew it would kill her right along with him. But with her singing him to sleep like she oftentimes did, at least he could go out somewhat happily. "It'll be good."
Her song choice was both happy and miserable. The part in the musical that it came from showed Marius at his most raw; most desolate state in the whole thing. The thought of his sister in that state broke Ollie's barely-beating heart in pieces.
But... Cosette had saved his life. His head turned to glance at David where he stood in the door. You'll be her Cosette, won't you? he asked in his mind. Since I can't take care of her anymore, you'll do it for me... And he knew that David would. She'd be broken, but he'd fix her. He'd take care of her.
She'd be okay. Someday.
"Oh my friends, my friends, don't ask me what your sacrifice was for..." was the last thing he heard, before everything faded into blackness.