Umm... No offense but it's obviously a fully different model in DCB. Anyone can tell that it is as her blood splatters are more pronounced in game, her face looks nothing like Mio's aside from the intentional resemblance, plus she has brand new animations when you fight her which in and of itself shows it's not the same model as it had to be redone to correctly utilize those animations.
You can tell because in this cutscene her model is more detailed in everything. And yes this cutscene is real time. You can tell because the character's eyes aren't reflective like they are in the CGI cutscenes, and the edges of things like their lips, fingers, nose, etc are of a lower quality than the ones in both types of CGI cutscenes in the game.
It's a completely new model.
Also I'm sorry but anyone who knows how to model things can create their own models and change them to look like a skin of another character. That's what Benja did for the Project Mayu patch and the animations of the characters look just like they do when played normally despite having a new skin.
And it's hardly fair to compare a CG promotional artwork rip of the original game to the new model.
Also there are more blood splatters on the right side of Sae's DCB kimono showing that it's a redone model there. Really there wouldn't even be much they needed to update there aside from adding a bit more blood splatter (which they did), and adding a few more seams and detail to her clothes (which they also did to the upper parts.)
And lastly (since I know this is the reason you believe this) a remake does not to be made fully from the ground up in every minute detail. Many remakes (even flat out new games) reuse art textures, or have some files leftover from the original version. Just because Resident Evil remake had every tiny thing remade from the ground up (supposedly) doesn't mean that something can't be a remake if it isn't made entirely from the ground up.
For more proof you can see in this cutscene that the bottom half of the model is clearly not the same in the remake. http://youtu.be/EStA2jfnQDM
Other video won't link so look it up on your own please.
As can clearly be seen, this isn't the same model in any aspect.