"Sam is so heartless, she never cared about Hannah-"
I believe that Sam loved Hannah so deeply and so much that when she died Sam couldn't handle even the mention of her name. I think the others said something about Hannah after the prank that had made Sam react badly enough that they didn't dare say her name around her even a year later. Not that it mattered cause it seems she cut contact with them after the prank anyway.
I believe the reason why Chris even brought up butterflies in the first place was to give Sam the room to speak about Hannah before they're around the others and she knew it but acted like she didn't. Because if she got into talking about Hannah right then , she wouldn't be able to stay strong during the rest of the time up there.
And Maybe that's why Josh did what he did to her. Maybe he was angry she wasn't mourning like him, when she wasn't talking about the twins like he was.Maybe he fell in that belief that she didn't care like he did.
I think that Sam loved Hannah so much, that even when she is caught by Hanndigo she still finds comfort in seeing the traces of Hannah in Hanndigo.
If Hanndigo had used Hannah's voice once we would have seen Sam crack hard.
