By all accounts, it wasn't a translation "error" that made her Aeris in the English translation. It was a change, but not one made by mistake. Kind of like how the Last Elixir became Megalixir, Mash became Sabin, and so forth.
Aerith is still her original name, though, and since since subsequent English-language products call her Aerith too, then that's arguably her official English name now.