I know, right? The earlier versions of Snow Queen/Frozen, concocted during the Eisner era, as I understand it, tried to turn the tale into a romance. A sort of "Taming of the Shrew" thing. I'm soooooooo glad Disney didn't go with that. But just the same, I will be forever puzzled as to why it threw out every single character in the original story because it "couldn't make it work". No, wait, scratch that. I know exactly why the Disney crew did what it did: The writers of Frozen were afraid of having a film star a little boy and girl. Not marketable enough. There HAD to be a princess in there somewhere. They were also scared of the much-maligned (by bitter feminists and "elite" film snobs) Disney Prince motif, where the girl is rescued by the guy. Now it so happens that in the Anderson Snow Queen story, the GIRL rescues the GUY. Problem solved, right? But NO, she's not a PRINCESS, so hey, forget that, the marketing department will kill us!
And then one of the writers, who just HAPPENED to be involved with "Wicked", came up with the sisters schtick. Because the misunderstood bad girl/good girl gimmick had worked so well with that show. As a result, a very contrived, very cynical, and very politically correct story was concocted. And all of the strong female characters from Anderson's century-old tale were jettisoned. Because, although they were strong, they weren't marketable.
But oh well, the movie's a HUGE hit, and so they all lived happily ever after.