It's been confirmed not to be Ellie, anyway she doesn't have the tattoos as in the first trailer.
I think it's likely Anna, Ellie's mum. They've implied parts of the story could take place in other time periods and the woman in the trailer is said to be pregnant, hence the (attempted) cutting of the stomach. They've also blanked out this character's name on pictures on Twitter, but revealed the other new character's names, I don't imagine why they'd do so unless it was Ellie's mum. 4 character name too.