In Japan, she's known as Aero; for the rest of the world, it's Sephira.
Mega Man Legends 3's newest heroine has developed quite a following already, and there's been many opinions about her name. Well aware of the matter, Capcom is officially seeking input: Should this new character be named Aero or Sephira in the US release of Mega Man Legends 3?
You can vote on which name you prefer at Capcom Unity. As noted by the US devroom's new liaison, GregaMan, there's no guarantee that they'll change the name, but the results may affect the final decision.
As of this writing, Aero leads the poll at 62%, with Sephira at 32%. Cast your vote here!
Source: Capcom Unity