1) Much like a butterface, except instead of liking all of her "but her face," he likes all of her except for everything about her. Hence, "but her her."
2) A girl that's so unattractive in every way, that a guy would not consider doing anything romantic with her, ever, because they don't yet have paper bags that cover the whole body.
(Ex 1) Guy: See that? I'm liking all of that butterher.
(Ex 2) Guy 1: There's this girl in my _____ class who is like the opposite of attractive.
Guy 2: Is she at least a butterface?
Guy 3: No man, I know the girl he's talking about, I wouldn't even get near that, she's more like a, a...
Guy 1: ...butterher.
Guy 2: Awwwwwww...