Paraphrasing what I posted at the poll: Maybe Elsa was born on the night of the Winter Solstice (December in the Northern Hemisphere) during the Aurora Borealis and was somehow touched por the magic of their lights, and that's how she got their powers. I'll bet Anna was born in spring or summer.
When you think about it, the opening song Frozen - Uma Aventura Congelante coração just foreshadows every bit of the movie. "Watch your step! Let it go! Ice has a magic can't be controlled! Stronger than one! Stronger than ten! Stronger than a hundred men!" and "This icy hold both foul and fair has a Frozen - Uma Aventura Congelante coração worth mining. Cut through the heart. Cold and clear. Strike for amor and strike for fear! There's beauty and there's danger here. dividido, dividir the ice apart! Beware the Frozen - Uma Aventura Congelante heart..."
The ice harvesters also start the song por saying "Born of cold and winter air and mountain rain combining." The only clue we really have of her birth in the movie, really. I imagine some sort of winter magic or aligning of cold elements gave Elsa her powers. Maybe it was during a snow storm with magic shards flying around or something, but I wonder: what's mais magical than the longest night of winter coupled with the Aurora Borealis?
Not only that, but Rapunzel got her healing powers from the sun. A drop of sunlight fell from the heavens, became a magic flower, her mother drank the flower, and the power flowed into her. While not quite as peaceful a power as healing all wounds, I imagine some indirect elemental magic flowed into Elsa to give her her elemental magic. Magic lights from the Aurora Borealis?
(Plus, a brief cameo of short-haired Rapunzel and Eugene showing up to queen Elsa's coronation, coupled with the two movies' similar art styles and fantasia settings, have led people to theorize it takes place in the same universe. Not only that, but that Rapunzel and Anna's similar appearance, coupled with Rapunzel's mom and Anna's/Elsa's mother having similar designs, have led people to further speculate that the girls might be related. Maybe their mothers are sisters or cousins?)
I've hammered this início enough. There could be some other reasons. (Earlier drafts and one throw-away line from her father in the movie indicates that their kingdom prophesized a curse and they believe Elsa is that curse based on her powers.) But I like this one.
