Who is the elf from ESO trailers

She's an Altmer returning from the original cinematic trailer series for the base game (she's technically the only survivor of the three heroes, if you ignore the Nord's implied imprisonment in Coldharbour). Similar to the original trailers, she's acting as a stand-in replacement for a potential player character, similar to how the Warden in the Morrowind cinematic trailer worked with Naryu (while also representing the new class introduced with Morrowind).

And yes, she's supposed to be an Altmer, not a Bosmer. The Khajiit is indeed Razum-dar, and the other party members are just red shirts without red shirts.