They show what she looked like before the events of the game, as well. More than once, if I remember correctly.
There's a post on their twitter somewhere confirming the validity of the pic. I'll put it in the original post in a min.
All video game characters have to be memorable or have a unique appearance, especially in Square Enix games. They might have changed her appearance because the real Shiki didn't have anything special about her.
But her plainness was the epitome of her character arc (literally, the first 7 days were based around that), I'm not saying it's not her, but it probably isn't the TWEWY1 Shiki.
I put that part on a different line to try to emphasize a different theory (though I guess I didn't make it clear enough).
That...actually makes quite a bit of sense. It would explain why she has a Mr.Mew, as well as why she seems to be wearing those niche, fashion clothes (possibly made by Shiki). Then there's the headphones, which...I'm not so sure about yet, but it's not unlikely that Eri grew her hair out and dyed it. That said, we don't actually know much about Eri, and the headphones do make me wonder if it's an existing character at all, reason being that, in Neku's case, the headphones represented isolation and the music represented the variation and the diverity of the world that he was left out of due to his repulsion of the thousands upon thousands of other worlds, the worlds that made Shibuya so unique. My point being, I think they are there to raise some type of point and what we know of Eri seems to suggest that she is comfortable with herself, though there is the chance that it's a false front and, say, she is only comforted when around Shiki, thus, she wears the headphones to create a false comfort that is provided when Shiki isn't around (though that's just a possible scenario). One could also take the fact that her hand is over her mouth to have some type of meaning.
