Secret way to save Aeris

Yeah, I found a secret way to stop Sephiroth from killing her.

There's another way. In the English version, from the beginning of the game, you have to be completely horrible to Tifa and wonderful to Aeris. Avoid every opportunity to be nice to Tifa. If given the choice, always leave Tifa behind and take Aeris with you. If you can be nice to Aeris, by all means, do it. Even if it means making the game more difficult to play, do it. If you do this right, when Sephiroth comes down to stab Aeris, Tifa will push her out of the way and Tifa will die instead of Aeris.