What is the name of the heroine in Amnesia?
She is only known as "Heroine." Now, if you look at Wikipedia or any other source and check the dates, you'll see that the anime is released after the game.

If the developers of the game never named her, e.g. implying the "Heroine" is whomever plays as her in the game, they didn't need to name her. This would allow the players to insert themselves into the game as the game's "Heroine."

So the fact that she isn't named could be entirely intentional in the game and the decision was carried over to the anime. If she didn't need a name in the game, I guess she didn't need it in the anime.

Wikipedia: http://en.wikipedia.org/wiki/Amnesia_(visual_novel)